diff --git a/.travis.yml b/.travis.yml
index 2a1ce51e..03de1047 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,22 +2,6 @@ language: cpp
 
 jobs:
  include:
-  - os: linux
-    name: Qt 4.8
-    dist: trusty
-    addons:
-      apt:
-        sources:
-          - sourceline: "ppa:beineri/opt-qt487-trusty"
-        packages:
-          - opt-qt4-qmake opt-qt4-dev-tools opt-libqt4-dev opt-libqt4-dev-bin opt-libqt4-opengl-dev
-    compiler: gcc
-    script:
-     - source /opt/qt*/bin/qt*-env.sh
-     - qmake PREFIX=/usr -v
-     - qmake PREFIX=/usr
-     - make -j$(nproc)
-    
   - os: linux
     name: Linux amd64
     dist: trusty
diff --git a/common/camera.cpp b/common/camera.cpp
index 30f53483..e8d64ae3 100644
--- a/common/camera.cpp
+++ b/common/camera.cpp
@@ -126,11 +126,7 @@ void lcCamera::CreateName(const lcArray<lcCamera*>& Cameras)
 		if (CameraName.startsWith(Prefix))
 		{
 			bool Ok = false;
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 			int CameraNumber = CameraName.midRef(Prefix.size()).toInt(&Ok);
-#else
-			int CameraNumber = CameraName.mid((int)strlen(Prefix.latin1())).toInt(&Ok);
-#endif
 
 			if (Ok && CameraNumber > MaxCameraNumber)
 				MaxCameraNumber = CameraNumber;
diff --git a/common/lc_application.cpp b/common/lc_application.cpp
index 5c626edd..9f22cc9a 100644
--- a/common/lc_application.cpp
+++ b/common/lc_application.cpp
@@ -140,10 +140,7 @@ void lcPreferences::SetInterfaceColors(lcColorTheme ColorTheme)
 lcApplication::lcApplication(int& Argc, char** Argv)
 	: QApplication(Argc, Argv)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	setApplicationDisplayName("LeoCAD");
-#endif
-
 	setOrganizationDomain("leocad.org");
 	setOrganizationName("LeoCAD Software");
 	setApplicationName("LeoCAD");
diff --git a/common/lc_global.h b/common/lc_global.h
index 1fdbafd3..d2ce94cf 100644
--- a/common/lc_global.h
+++ b/common/lc_global.h
@@ -9,6 +9,7 @@
 #include <QGLWidget>
 #include <QtGui>
 #include <QPrinter>
+#include <QtConcurrent>
 #include <map>
 #include <vector>
 #include <array>
diff --git a/common/lc_library.cpp b/common/lc_library.cpp
index 5be7b2b4..a202bead 100644
--- a/common/lc_library.cpp
+++ b/common/lc_library.cpp
@@ -16,9 +16,7 @@
 #include <ctype.h>
 #include <locale.h>
 #include <zlib.h>
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 #include <QtConcurrent>
-#endif
 
 #if MAX_MEM_LEVEL >= 8
 #  define DEF_MEM_LEVEL 8
@@ -33,12 +31,8 @@
 lcPiecesLibrary::lcPiecesLibrary()
 	: mLoadMutex(QMutex::Recursive)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QStringList cachePathList = QStandardPaths::standardLocations(QStandardPaths::CacheLocation);
 	mCachePath = cachePathList.first();
-#else
-	mCachePath  = QDesktopServices::storageLocation(QDesktopServices::CacheLocation);
-#endif
 
 	QDir Dir;
 	Dir.mkpath(mCachePath);
@@ -426,19 +420,12 @@ void lcPiecesLibrary::ReadArchiveDescriptions(const QString& OfficialFileName, c
 	QFileInfo UnofficialInfo(UnofficialFileName);
 
 	mArchiveCheckSum[0] = OfficialInfo.size();
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 	mArchiveCheckSum[1] = OfficialInfo.lastModified().toMSecsSinceEpoch();
-#else
-	mArchiveCheckSum[1] = OfficialInfo.lastModified().toTime_t();
-#endif
+
 	if (!UnofficialFileName.isEmpty())
 	{
 		mArchiveCheckSum[2] = UnofficialInfo.size();
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		mArchiveCheckSum[3] = UnofficialInfo.lastModified().toMSecsSinceEpoch();
-#else
-		mArchiveCheckSum[3] = UnofficialInfo.lastModified().toTime_t();
-#endif
 	}
 	else
 	{
@@ -692,11 +679,7 @@ void lcPiecesLibrary::ReadDirectoryDescriptions(const QFileInfoList (&FileLists)
 				const char* Description = FileName + strlen(FileName) + 1;
 				const uint64_t CachedFileTime = *(uint64_t*)(Description + strlen(Description) + 1 + 4 + 1);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 				quint64 FileTime = FileLists[Info->mFolderType][Info->mFolderIndex].lastModified().toMSecsSinceEpoch();
-#else
-				quint64 FileTime = FileLists[Info->mFolderType][Info->mFolderIndex].lastModified().toTime_t();
-#endif
 
 				if (FileTime == CachedFileTime)
 				{
@@ -746,7 +729,7 @@ void lcPiecesLibrary::ReadDirectoryDescriptions(const QFileInfoList (&FileLists)
 
 	while (!LoadFuture.isFinished())
 	{
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0) || QT_VERSION < QT_VERSION_CHECK(5, 0, 0) )
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0))
 		ProgressDialog->setValue(FilesLoaded);
 #else
 		ProgressDialog->setValue(FilesLoaded.load());
@@ -754,7 +737,7 @@ void lcPiecesLibrary::ReadDirectoryDescriptions(const QFileInfoList (&FileLists)
 		QApplication::processEvents(QEventLoop::ExcludeUserInputEvents);
 	}
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0) || QT_VERSION < QT_VERSION_CHECK(5, 0, 0) )
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0))
 	ProgressDialog->setValue(FilesLoaded);
 #else
 	ProgressDialog->setValue(FilesLoaded.load());
@@ -793,11 +776,7 @@ void lcPiecesLibrary::ReadDirectoryDescriptions(const QFileInfoList (&FileLists)
 
 			NewIndexFile.WriteU8(Info->mFolderType);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 			quint64 FileTime = FileLists[Info->mFolderType][Info->mFolderIndex].lastModified().toMSecsSinceEpoch();
-#else
-			quint64 FileTime = FileLists[Info->mFolderType][Info->mFolderIndex].lastModified().toTime_t();
-#endif
 
 			NewIndexFile.WriteU64(FileTime);
 		}
diff --git a/common/lc_mainwindow.cpp b/common/lc_mainwindow.cpp
index d5005d98..2884c6b3 100644
--- a/common/lc_mainwindow.cpp
+++ b/common/lc_mainwindow.cpp
@@ -50,14 +50,6 @@ void lcTabBar::mouseReleaseEvent(QMouseEvent* Event)
 		QTabBar::mouseReleaseEvent(Event);
 }
 
-lcTabWidget::lcTabWidget()
-	: QTabWidget()
-{
-	lcTabBar* TabBar = new lcTabBar(this);
-	setTabBar(TabBar);
-	TabBar->setDrawBase(false);
-}
-
 void lcModelTabWidget::ResetLayout()
 {
 	QLayout* TabLayout = layout();
@@ -147,19 +139,14 @@ void lcMainWindow::CreateWidgets()
 	CreateMenus();
 	CreateStatusBar();
 
-	mModelTabWidget = new lcTabWidget();
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
+	mModelTabWidget = new QTabWidget();
 	mModelTabWidget->tabBar()->setMovable(true);
 	mModelTabWidget->tabBar()->setTabsClosable(true);
 	mModelTabWidget->tabBar()->setContextMenuPolicy(Qt::CustomContextMenu);
+	setCentralWidget(mModelTabWidget);
+
 	connect(mModelTabWidget->tabBar(), SIGNAL(tabCloseRequested(int)), this, SLOT(ModelTabClosed(int)));
 	connect(mModelTabWidget->tabBar(), SIGNAL(customContextMenuRequested(const QPoint&)), this, SLOT(ModelTabContextMenuRequested(const QPoint&)));
-#else
-	mModelTabWidget->setMovable(true);
-	mModelTabWidget->setTabsClosable(true);
-	connect(mModelTabWidget, SIGNAL(tabCloseRequested(int)), this, SLOT(ModelTabClosed(int)));
-#endif
-	setCentralWidget(mModelTabWidget);
 	connect(mModelTabWidget, SIGNAL(currentChanged(int)), this, SLOT(ModelTabChanged(int)));
 
 	connect(QApplication::clipboard(), SIGNAL(dataChanged()), this, SLOT(ClipboardChanged()));
@@ -463,9 +450,7 @@ void lcMainWindow::CreateMenus()
 	FileMenu->addAction(mActions[LC_FILE_SAVE_IMAGE]);
 	QMenu* ImportMenu = FileMenu->addMenu(tr("&Import"));
 	ImportMenu->addAction(mActions[LC_FILE_IMPORT_LDD]);
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	ImportMenu->addAction(mActions[LC_FILE_IMPORT_INVENTORY]);
-#endif
 	QMenu* ExportMenu = FileMenu->addMenu(tr("&Export"));
 	ExportMenu->addAction(mActions[LC_FILE_EXPORT_3DS]);
 	ExportMenu->addAction(mActions[LC_FILE_EXPORT_BRICKLINK]);
@@ -1150,15 +1135,11 @@ void lcMainWindow::Print(QPrinter* Printer)
 	if (Printer->collateCopies())
 	{
 		DocCopies = 1;
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		PageCopies = Printer->supportsMultipleCopies() ? 1 : Printer->copyCount();
-#endif
 	}
 	else
 	{
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		DocCopies = Printer->supportsMultipleCopies() ? 1 : Printer->copyCount();
-#endif
 		PageCopies = 1;
 	}
 
diff --git a/common/lc_mainwindow.h b/common/lc_mainwindow.h
index 1fb99e61..97ebae38 100644
--- a/common/lc_mainwindow.h
+++ b/common/lc_mainwindow.h
@@ -46,19 +46,6 @@ protected:
 	int mMousePressTab;
 };
 
-class lcTabWidget : public QTabWidget
-{
-public:
-	lcTabWidget();
-
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-	QTabBar* tabBar()
-	{
-		return QTabWidget::tabBar();
-	}
-#endif
-};
-
 class lcModelTabWidget : public QWidget
 {
 	Q_OBJECT
@@ -431,7 +418,7 @@ protected:
 
 	QAction* mActionFileRecentSeparator;
 
-	lcTabWidget* mModelTabWidget;
+	QTabWidget* mModelTabWidget;
 	QToolBar* mStandardToolBar;
 	QToolBar* mToolsToolBar;
 	QToolBar* mTimeToolBar;
diff --git a/common/lc_mesh.h b/common/lc_mesh.h
index dc789f8e..22e25499 100644
--- a/common/lc_mesh.h
+++ b/common/lc_mesh.h
@@ -48,11 +48,7 @@ enum
 	LC_NUM_MESH_LODS
 };
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 enum class lcMeshFlag
-#else
-enum lcMeshFlag
-#endif
 {
 	HasDefault     = 0x01, // Mesh has triangles using the default color
 	HasSolid       = 0x02, // Mesh has triangles using a solid color
diff --git a/common/lc_minifigdialog.cpp b/common/lc_minifigdialog.cpp
index 7973c537..5599b63b 100644
--- a/common/lc_minifigdialog.cpp
+++ b/common/lc_minifigdialog.cpp
@@ -88,10 +88,6 @@ lcMinifigDialog::lcMinifigDialog(QWidget* Parent)
 		ColorPicker->blockSignals(false);
 	}
 
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-	ui->TemplateGroup->hide();
-#endif
-
 	UpdateTemplateCombo();
 
 	mMinifigWizard->Calculate();
@@ -116,7 +112,6 @@ void lcMinifigDialog::UpdateTemplateCombo()
 
 void lcMinifigDialog::on_TemplateComboBox_currentIndexChanged(const QString& TemplateName)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	const auto& Templates = mMinifigWizard->GetTemplates();
 	const auto& Position = Templates.find(TemplateName);
 	if (Position == Templates.end())
@@ -155,12 +150,10 @@ void lcMinifigDialog::on_TemplateComboBox_currentIndexChanged(const QString& Tem
 	}
 
 	mMinifigWizard->Calculate();
-#endif
 }
 
 void lcMinifigDialog::on_TemplateSaveButton_clicked()
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QString CurrentName = ui->TemplateComboBox->currentText();
 	bool Ok;
 	QString TemplateName = QInputDialog::getText(this, tr("Save Template"), tr("Template Name:"), QLineEdit::Normal, CurrentName, &Ok);
@@ -197,7 +190,6 @@ void lcMinifigDialog::on_TemplateSaveButton_clicked()
 	UpdateTemplateCombo();
 	ui->TemplateComboBox->setCurrentText(TemplateName);
 	ui->TemplateComboBox->blockSignals(false);
-#endif
 }
 
 void lcMinifigDialog::on_TemplateDeleteButton_clicked()
diff --git a/common/lc_model.cpp b/common/lc_model.cpp
index 61be624b..722552ad 100644
--- a/common/lc_model.cpp
+++ b/common/lc_model.cpp
@@ -25,9 +25,6 @@
 #include "lc_qutils.h"
 #include "lc_lxf.h"
 #include "lc_previewwidget.h"
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-#include <QtConcurrent>
-#endif
 
 void lcModelProperties::LoadDefaults()
 {
@@ -974,7 +971,6 @@ bool lcModel::LoadLDD(const QString& FileData)
 
 bool lcModel::LoadInventory(const QByteArray& Inventory)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QJsonDocument Document = QJsonDocument::fromJson(Inventory);
 	QJsonObject Root = Document.object();
 	QJsonArray Parts = Root["results"].toArray();
@@ -1048,9 +1044,6 @@ bool lcModel::LoadInventory(const QByteArray& Inventory)
 	CalculateStep(mCurrentStep);
 
 	return true;
-#else
-	return false;
-#endif
 }
 
 void lcModel::Merge(lcModel* Other)
diff --git a/common/lc_partpalettedialog.cpp b/common/lc_partpalettedialog.cpp
index f7e33021..62d61fbc 100644
--- a/common/lc_partpalettedialog.cpp
+++ b/common/lc_partpalettedialog.cpp
@@ -9,10 +9,6 @@ lcPartPaletteDialog::lcPartPaletteDialog(QWidget* Parent, std::vector<lcPartPale
 {
     ui->setupUi(this);
 
-#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
-	ui->ImportButton->hide();
-#endif
-
 	for (const lcPartPalette& Palette : PartPalettes)
 	{
 		QListWidgetItem* Item = new QListWidgetItem(Palette.Name);
@@ -128,7 +124,6 @@ void lcPartPaletteDialog::on_ImportButton_clicked()
 	Palette->Name = Dialog.GetSetDescription();
 	mImportedPalettes.push_back(Palette);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QByteArray Inventory = Dialog.GetSetInventory();
 	QJsonDocument Document = QJsonDocument::fromJson(Inventory);
 	QJsonObject Root = Document.object();
@@ -144,7 +139,6 @@ void lcPartPaletteDialog::on_ImportButton_clicked()
 
 		Palette->Parts.push_back(PartID.toUpper().toStdString() + ".DAT");
 	}
-#endif
 
 	QListWidgetItem* Item = new QListWidgetItem(Palette->Name);
 	Item->setData(Qt::UserRole, QVariant::fromValue<uintptr_t>(reinterpret_cast<uintptr_t>(Palette)));
diff --git a/common/lc_partselectionwidget.cpp b/common/lc_partselectionwidget.cpp
index 83f8ef82..9a8b3a39 100644
--- a/common/lc_partselectionwidget.cpp
+++ b/common/lc_partselectionwidget.cpp
@@ -550,9 +550,7 @@ lcPartSelectionListView::lcPartSelectionListView(QWidget* Parent, lcPartSelectio
 	lcPartSelectionItemDelegate* ItemDelegate = new lcPartSelectionItemDelegate(this, mListModel);
 	setItemDelegate(ItemDelegate);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	connect(this, SIGNAL(customContextMenuRequested(QPoint)), SLOT(CustomContextMenuRequested(QPoint)));
-#endif
 
 	SetIconSize(lcGetProfileInt(LC_PROFILE_PARTS_LIST_ICONS));
 }
@@ -1013,7 +1011,6 @@ void lcPartSelectionWidget::SetDefaultPart()
 
 void lcPartSelectionWidget::LoadPartPalettes()
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QByteArray Buffer = lcGetProfileBuffer(LC_PROFILE_PART_PALETTES);
 	QJsonDocument Document = QJsonDocument::fromJson(Buffer);
 
@@ -1044,12 +1041,10 @@ void lcPartSelectionWidget::LoadPartPalettes()
 
 		mPartPalettes.emplace_back(std::move(Palette));
 	}
-#endif
 }
 
 void lcPartSelectionWidget::SavePartPalettes()
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QJsonObject RootObject;
 
 	RootObject["Version"] = 1;
@@ -1069,7 +1064,6 @@ void lcPartSelectionWidget::SavePartPalettes()
 
 	QByteArray Buffer = QJsonDocument(RootObject).toJson();
 	lcSetProfileBuffer(LC_PROFILE_PART_PALETTES, Buffer);
-#endif
 }
 
 void lcPartSelectionWidget::AddToPalette()
diff --git a/common/lc_shortcuts.cpp b/common/lc_shortcuts.cpp
index 3e1c8b41..00f34485 100644
--- a/common/lc_shortcuts.cpp
+++ b/common/lc_shortcuts.cpp
@@ -139,15 +139,10 @@ void lcMouseShortcuts::Reset()
 	RotateViewShortcut.Button2 = Qt::RightButton;
 
 	lcToolShortcut& PanShortcut = mShortcuts[static_cast<int>(lcTool::Pan)];
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 	PanShortcut.Modifiers1 = Qt::AltModifier;
 	PanShortcut.Button1 = Qt::MiddleButton;
 	PanShortcut.Modifiers2 = Qt::ShiftModifier;
 	PanShortcut.Button2 = Qt::RightButton;
-#else
-	PanShortcut.Modifiers1 = Qt::ShiftModifier;
-	PanShortcut.Button1 = Qt::RightButton;
-#endif
 
 	lcToolShortcut& ZoomShortcut = mShortcuts[static_cast<int>(lcTool::Zoom)];
 	ZoomShortcut.Modifiers1 = Qt::AltModifier;
diff --git a/common/lc_texture.h b/common/lc_texture.h
index 9579bf84..6f7c753d 100644
--- a/common/lc_texture.h
+++ b/common/lc_texture.h
@@ -41,7 +41,7 @@ public:
 	{
 		mRefCount.ref();
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0) || QT_VERSION < QT_VERSION_CHECK(5, 0, 0) )
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 3, 0))
 		if (mRefCount == 1)
 #else
 		if (mRefCount.load() == 1)
diff --git a/common/lc_view.cpp b/common/lc_view.cpp
index 698ab78b..820ded92 100644
--- a/common/lc_view.cpp
+++ b/common/lc_view.cpp
@@ -3333,7 +3333,6 @@ void lcView::OnMiddleButtonDown()
 		return;
 	}
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 	lcTrackTool OverrideTool = GetOverrideTrackTool(Qt::MiddleButton);
 
 	if (OverrideTool != lcTrackTool::None)
@@ -3341,7 +3340,7 @@ void lcView::OnMiddleButtonDown()
 		mTrackTool = OverrideTool;
 		UpdateCursor();
 	}
-#endif
+
 	OnButtonDown(lcTrackButton::Middle);
 }
 
diff --git a/common/lc_viewwidget.cpp b/common/lc_viewwidget.cpp
index c48993fe..fca54c76 100644
--- a/common/lc_viewwidget.cpp
+++ b/common/lc_viewwidget.cpp
@@ -145,7 +145,6 @@ void lcViewWidget::mousePressEvent(QMouseEvent* MouseEvent)
 		mView->OnRightButtonDown();
 		break;
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	case Qt::BackButton:
 		mView->OnBackButtonDown();
 		break;
@@ -153,7 +152,6 @@ void lcViewWidget::mousePressEvent(QMouseEvent* MouseEvent)
 	case Qt::ForwardButton:
 		mView->OnForwardButtonDown();
 		break;
-#endif
 
 	default:
 		break;
@@ -181,7 +179,6 @@ void lcViewWidget::mouseReleaseEvent(QMouseEvent* MouseEvent)
 		mView->OnRightButtonUp();
 		break;
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	case Qt::BackButton:
 		mView->OnBackButtonUp();
 		break;
@@ -189,7 +186,6 @@ void lcViewWidget::mouseReleaseEvent(QMouseEvent* MouseEvent)
 	case Qt::ForwardButton:
 		mView->OnForwardButtonUp();
 		break;
-#endif
 
 	default:
 		break;
diff --git a/common/lc_viewwidget.h b/common/lc_viewwidget.h
index 488387da..3213953c 100644
--- a/common/lc_viewwidget.h
+++ b/common/lc_viewwidget.h
@@ -28,10 +28,8 @@ protected:
 	{
 #ifdef LC_USE_QOPENGLWIDGET
 		return devicePixelRatio();
-#elif (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-		return windowHandle()->devicePixelRatio();
 #else
-		return 1.0f;
+		return windowHandle()->devicePixelRatio();
 #endif
 	}
 
diff --git a/common/light.cpp b/common/light.cpp
index 3f7afc64..affeb0b6 100644
--- a/common/light.cpp
+++ b/common/light.cpp
@@ -81,11 +81,7 @@ void lcLight::CreateName(const lcArray<lcLight*>& Lights)
 		if (LightName.startsWith(Prefix))
 		{
 			bool Ok = false;
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 			int LightNumber = LightName.midRef(Prefix.size()).toInt(&Ok);
-#else
-			int LightNumber = LightName.mid((int)strlen(Prefix.latin1())).toInt(&Ok);
-#endif
 
 			if (Ok && LightNumber > MaxLightNumber)
 				MaxLightNumber = LightNumber;
diff --git a/common/minifig.cpp b/common/minifig.cpp
index 538dcb2e..e84ffb01 100644
--- a/common/minifig.cpp
+++ b/common/minifig.cpp
@@ -204,7 +204,6 @@ void MinifigWizard::DeleteTemplate(const QString& TemplateName)
 
 void MinifigWizard::AddTemplatesJson(const QByteArray& TemplateData)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QJsonDocument Document = QJsonDocument::fromJson(TemplateData);
 	QJsonObject RootObject = Document.object();
 
@@ -235,17 +234,10 @@ void MinifigWizard::AddTemplatesJson(const QByteArray& TemplateData)
 
 		mTemplates.emplace(ElementIt.key(), std::move(Template));
 	}
-#endif
 }
 
 QByteArray MinifigWizard::GetTemplatesJson() const
 {
-	QByteArray TemplateData;
-
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-	QJsonObject RootObject;
-
-	RootObject["Version"] = 1;
 	QJsonObject TemplatesObject;
 
 	for (const auto& TemplateEntry : mTemplates)
@@ -267,11 +259,11 @@ QByteArray MinifigWizard::GetTemplatesJson() const
 		TemplatesObject[TemplateEntry.first] = TemplateObject;
 	}
 
+	QJsonObject RootObject;
 	RootObject["Templates"] = TemplatesObject;
-	TemplateData = QJsonDocument(RootObject).toJson();
-#endif
+	RootObject["Version"] = 1;
 
-	return TemplateData;
+	return QJsonDocument(RootObject).toJson();
 }
 
 void MinifigWizard::LoadTemplates()
@@ -287,11 +279,9 @@ void MinifigWizard::LoadTemplates()
 
 void MinifigWizard::SaveTemplates()
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	QSettings Settings;
 	Settings.beginGroup("Minifig");
 	Settings.setValue("Templates", GetTemplatesJson());
-#endif
 }
 
 void MinifigWizard::Calculate()
diff --git a/common/project.cpp b/common/project.cpp
index 1a32657a..c178d1d6 100644
--- a/common/project.cpp
+++ b/common/project.cpp
@@ -124,12 +124,8 @@ QString Project::GetImageFileName(bool AllowCurrentFolder) const
 			FileName = QLatin1String("image");
 		else
 		{
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-			QStringList cachePathList = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);
-			FileName = cachePathList.first();
-#else
-			FileName = QDesktopServices::storageLocation(QDesktopServices::DocumentsLocation);
-#endif
+			QStringList CachePathList = QStandardPaths::standardLocations(QStandardPaths::DocumentsLocation);
+			FileName = CachePathList.first();
 			FileName = QDir(FileName).absoluteFilePath(QLatin1String("image"));
 		}
 	}
diff --git a/leocad.pro b/leocad.pro
index 466984ea..8fb27444 100644
--- a/leocad.pro
+++ b/leocad.pro
@@ -1,16 +1,14 @@
-QT += core gui opengl network xml
+QT += core gui opengl network xml concurrent
+QT *= printsupport
 TEMPLATE = app
 
-greaterThan(QT_MAJOR_VERSION, 4) {
-	QT *= printsupport
-	QT += concurrent
+lessThan(QT_MAJOR_VERSION, 5) {
+	error("LeoCAD requires Qt5 or later.")
 }
 
-equals(QT_MAJOR_VERSION, 5) {
-	qtHaveModule(gamepad) {
-		QT += gamepad
-		DEFINES += LC_ENABLE_GAMEPAD
-	}
+qtHaveModule(gamepad) {
+	QT += gamepad
+	DEFINES += LC_ENABLE_GAMEPAD
 }
 
 INCLUDEPATH += qt common
@@ -32,14 +30,10 @@ win32-msvc* {
 	QMAKE_CXXFLAGS_WARN_ON += -wd4100
 	QMAKE_CXXFLAGS *= /MP /W4
 	PRECOMPILED_HEADER = common/lc_global.h
-	DEFINES += _CRT_SECURE_NO_WARNINGS _CRT_SECURE_NO_DEPRECATE=1 _CRT_NONSTDC_NO_WARNINGS=1
-	greaterThan(QT_MAJOR_VERSION, 4) {
-		INCLUDEPATH += $$[QT_INSTALL_HEADERS]/QtZlib
-	} else {
-		INCLUDEPATH += $$[QT_INSTALL_PREFIX]/src/3rdparty/zlib
-	}
-	QMAKE_LFLAGS += /INCREMENTAL
 	PRECOMPILED_SOURCE = common/lc_global.cpp
+	DEFINES += _CRT_SECURE_NO_WARNINGS _CRT_SECURE_NO_DEPRECATE=1 _CRT_NONSTDC_NO_WARNINGS=1
+	INCLUDEPATH += $$[QT_INSTALL_HEADERS]/QtZlib
+	QMAKE_LFLAGS += /INCREMENTAL
 	LIBS += -ladvapi32 -lshell32 -lopengl32 -luser32
 } else {
 	PRECOMPILED_HEADER = common/lc_global.h
@@ -47,17 +41,6 @@ win32-msvc* {
 	QMAKE_CXXFLAGS_WARN_ON += -Wno-unused-parameter
 }
 
-lessThan(QT_MAJOR_VERSION, 5) {
-	unix {
-		GCC_VERSION = $$system(g++ -dumpversion)
-		greaterThan(GCC_VERSION, 4.6) {
-			QMAKE_CXXFLAGS += -std=c++11
-		} else {
-			QMAKE_CXXFLAGS += -std=c++0x
-		}
-	}
-}
-
 isEmpty(QMAKE_LRELEASE) {
 	win32:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]\\lrelease.exe
 	else:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]/lrelease
diff --git a/qt/lc_qpreferencesdialog.cpp b/qt/lc_qpreferencesdialog.cpp
index abb2a4fd..dd832bf5 100644
--- a/qt/lc_qpreferencesdialog.cpp
+++ b/qt/lc_qpreferencesdialog.cpp
@@ -229,15 +229,9 @@ lcQPreferencesDialog::lcQPreferencesDialog(QWidget* Parent, lcPreferencesDialogO
 	commandChanged(nullptr);
 
 	UpdateMouseTree();
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	ui->mouseTree->header()->setSectionResizeMode(0, QHeaderView::Stretch);
 	ui->mouseTree->header()->setSectionResizeMode(1, QHeaderView::ResizeToContents);
 	ui->mouseTree->header()->setSectionResizeMode(2, QHeaderView::ResizeToContents);
-#else
-	ui->mouseTree->header()->setResizeMode(0, QHeaderView::Stretch);
-	ui->mouseTree->header()->setResizeMode(1, QHeaderView::ResizeToContents);
-	ui->mouseTree->header()->setResizeMode(2, QHeaderView::ResizeToContents);
-#endif
 	MouseTreeItemChanged(nullptr);
 }
 
@@ -1068,11 +1062,9 @@ void lcQPreferencesDialog::UpdateMouseTreeItem(int ItemIndex)
 			Shortcut += tr("Left Button");
 			break;
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		case Qt::MiddleButton:
 			Shortcut += tr("Middle Button");
 			break;
-#endif
 
 		case Qt::RightButton:
 			Shortcut += tr("Right Button");
@@ -1117,11 +1109,9 @@ void lcQPreferencesDialog::on_mouseAssign_clicked()
 			Button = Qt::LeftButton;
 			break;
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		case 2:
 			Button = Qt::MiddleButton;
 			break;
-#endif
 
 		case 3:
 			Button = Qt::RightButton;
@@ -1262,11 +1252,9 @@ void lcQPreferencesDialog::MouseTreeItemChanged(QTreeWidgetItem* Current)
 		ui->mouseButton->setCurrentIndex(1);
 		break;
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 	case Qt::MiddleButton:
 		ui->mouseButton->setCurrentIndex(2);
 		break;
-#endif
 
 	case Qt::RightButton:
 		ui->mouseButton->setCurrentIndex(3);
diff --git a/qt/lc_qpropertiesdialog.cpp b/qt/lc_qpropertiesdialog.cpp
index 873af370..6d23f682 100644
--- a/qt/lc_qpropertiesdialog.cpp
+++ b/qt/lc_qpropertiesdialog.cpp
@@ -76,12 +76,7 @@ lcQPropertiesDialog::lcQPropertiesDialog(QWidget* Parent, lcPropertiesDialogOpti
 	table->setColumnCount(NumColors + 2);
 	table->setRowCount((int)PartsList.size() + 1);
 	table->setHorizontalHeaderLabels(horizontalLabels);
-
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	table->horizontalHeader()->setSectionResizeMode(QHeaderView::ResizeToContents);
-#else
-	table->horizontalHeader()->setResizeMode(QHeaderView::ResizeToContents);
-#endif
 
 	std::vector<int> InfoTotals(PartsList.size());
 	std::vector<int> ColorTotals(NumColors);
diff --git a/qt/lc_qpropertiestree.cpp b/qt/lc_qpropertiestree.cpp
index cbcffc85..46a0463d 100644
--- a/qt/lc_qpropertiestree.cpp
+++ b/qt/lc_qpropertiestree.cpp
@@ -211,13 +211,8 @@ lcQPropertiesTree::lcQPropertiesTree(QWidget *parent) :
 	labels.append(tr("Property"));
 	labels.append(tr("Value"));
 	setHeaderLabels(labels);
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	header()->setSectionsMovable(false);
 	header()->setSectionResizeMode(QHeaderView::ResizeToContents);
-#else
-	header()->setMovable(false);
-	header()->setResizeMode(QHeaderView::ResizeToContents);
-#endif
 	header()->setVisible(false);
 	setAlternatingRowColors(true);
 	setRootIsDecorated(false);
diff --git a/qt/lc_qupdatedialog.cpp b/qt/lc_qupdatedialog.cpp
index 7d749bb5..059dfaa3 100644
--- a/qt/lc_qupdatedialog.cpp
+++ b/qt/lc_qupdatedialog.cpp
@@ -20,11 +20,7 @@ void lcDoInitialUpdateCheck()
 	{
 		QDateTime NextCheckTime = CheckTime.addDays(updateFrequency == 1 ? 1 : 7);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		if (NextCheckTime > QDateTime::currentDateTimeUtc())
-#else
-		if (NextCheckTime > QDateTime::currentDateTime())
-#endif
 			return;
 	}
 
@@ -136,11 +132,7 @@ void lcQUpdateDialog::DownloadFinished(lcHttpReply *reply)
 		else
 			ui->status->setText(tr("Error parsing update information."));
 
-#if (QT_VERSION >= QT_VERSION_CHECK(4, 7, 0))
 		settings.setValue("Updates/LastCheck", QDateTime::currentDateTimeUtc());
-#else
-		settings.setValue("Updates/LastCheck", QDateTime::currentDateTime());
-#endif
 	}
 	else
 		ui->status->setText(tr("Error connecting to the update server."));
diff --git a/qt/lc_qutils.cpp b/qt/lc_qutils.cpp
index ffce15f0..dbfe26ae 100644
--- a/qt/lc_qutils.cpp
+++ b/qt/lc_qutils.cpp
@@ -60,36 +60,27 @@ bool lcQTreeWidgetColumnStretcher::eventFilter(QObject *obj, QEvent *ev)
 	{
 		if (ev->type() == QEvent::Show)
 		{
-			QHeaderView *hv = qobject_cast<QHeaderView*>(obj);
-			for (int i = 0; i < hv->count(); ++i)
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-				hv->setSectionResizeMode(i, QHeaderView::Interactive);
-#else
-				hv->setResizeMode(i, QHeaderView::Interactive);
-#endif
+			QHeaderView* HeaderView = qobject_cast<QHeaderView*>(obj);
+
+			for (int i = 0; i < HeaderView->count(); ++i)
+				HeaderView->setSectionResizeMode(i, QHeaderView::Interactive);
 		}
 		else if (ev->type() == QEvent::Hide)
 		{
-			QHeaderView *hv = qobject_cast<QHeaderView*>(obj);
-			for (int i = 0; i < hv->count(); ++i)
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-				hv->setSectionResizeMode(i, i == m_columnToStretch ? QHeaderView::Stretch : QHeaderView::ResizeToContents);
-#else
-				hv->setResizeMode(i, i == m_columnToStretch ? QHeaderView::Stretch : QHeaderView::ResizeToContents);
-#endif
+			QHeaderView* HeaderView = qobject_cast<QHeaderView*>(obj);
+
+			for (int i = 0; i < HeaderView->count(); ++i)
+				HeaderView->setSectionResizeMode(i, i == m_columnToStretch ? QHeaderView::Stretch : QHeaderView::ResizeToContents);
 		}
 		else if (ev->type() == QEvent::Resize)
 		{
-			QHeaderView *hv = qobject_cast<QHeaderView*>(obj);
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
-			if (hv->sectionResizeMode(m_columnToStretch) == QHeaderView::Interactive)
-#else
-			if (hv->resizeMode(m_columnToStretch) == QHeaderView::Interactive)
-#endif
+			QHeaderView* HeaderView = qobject_cast<QHeaderView*>(obj);
+
+			if (HeaderView->sectionResizeMode(m_columnToStretch) == QHeaderView::Interactive)
 			{
 				QResizeEvent *re = static_cast<QResizeEvent*>(ev);
 				int diff = re->size().width() - re->oldSize().width() ;
-				hv->resizeSection(m_columnToStretch, qMax(32, hv->sectionSize(1) + diff));
+				HeaderView->resizeSection(m_columnToStretch, qMax(32, HeaderView->sectionSize(1) + diff));
 			}
 		}
 	}
diff --git a/qt/lc_setsdatabasedialog.cpp b/qt/lc_setsdatabasedialog.cpp
index 43861629..3d7aa567 100644
--- a/qt/lc_setsdatabasedialog.cpp
+++ b/qt/lc_setsdatabasedialog.cpp
@@ -155,7 +155,6 @@ void lcSetsDatabaseDialog::on_SearchButton_clicked()
 
 void lcSetsDatabaseDialog::DownloadFinished(lcHttpReply* Reply)
 {
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
 	if (Reply == mKeyListReply)
 	{
 		if (!Reply->error())
@@ -227,7 +226,6 @@ void lcSetsDatabaseDialog::DownloadFinished(lcHttpReply* Reply)
 
 		mInventoryReply = nullptr;
 	}
-#endif
 
 	Reply->deleteLater();
 }