diff --git a/Changelog.md b/Changelog.md
index 6f2cf35..91f5bf7 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -9,6 +9,8 @@ Changelog
 - SonarCloud integration, Sonar way profile
 - clang-format now based on google style
 - [google c++ style guide](https://google.github.io/styleguide/cppguide.html) applied
+  - define guard
+  - name and order of inclusions
 - Test files are now markdown (.md) files, tests result are slightly changed
 - Delivery as flatpak and snap
 - it seems cosh was giving sinh  (!)
diff --git a/src/constant.h b/src/constant.h
index 084c96f..b1e1362 100644
--- a/src/constant.h
+++ b/src/constant.h
@@ -1,5 +1,5 @@
-#ifndef CONSTANT_H
-#define CONSTANT_H
+#ifndef CONSTANT_H_
+#define CONSTANT_H_
 
 #define MPFR_USE_NO_MACRO
 #include <mpfr.h>
diff --git a/src/escape.h b/src/escape.h
index ba20c2c..f279cb9 100644
--- a/src/escape.h
+++ b/src/escape.h
@@ -1,5 +1,5 @@
-#ifndef ESCAPE_H
-#define ESCAPE_H
+#ifndef ESCAPE_H_
+#define ESCAPE_H_
 
 // ANSI escape sequences
 
diff --git a/src/input.hpp b/src/input.hpp
index 55a7b23..5328a9c 100644
--- a/src/input.hpp
+++ b/src/input.hpp
@@ -1,5 +1,5 @@
-#ifndef _ENTRY_HPP_
-#define _ENTRY_HPP_
+#ifndef INPUT_HPP_
+#define INPUT_HPP_
 
 #include <string>
 #include <vector>
diff --git a/src/lexer.hpp b/src/lexer.hpp
index 34c4964..0b428ea 100644
--- a/src/lexer.hpp
+++ b/src/lexer.hpp
@@ -1,5 +1,5 @@
-#ifndef _PARSER_HPP_
-#define _PARSER_HPP_
+#ifndef LEXER_HPP_
+#define LEXER_HPP_
 
 #include <map>
 #include <vector>
diff --git a/src/mpreal-out.hpp b/src/mpreal-out.hpp
index f2e8e65..d007422 100644
--- a/src/mpreal-out.hpp
+++ b/src/mpreal-out.hpp
@@ -1,3 +1,6 @@
+#ifndef MPREAL_OUT_HPP_
+#define MPREAL_OUT_HPP_
+
 #include <string>
 #include <ostream>
 using namespace std;
@@ -9,3 +12,5 @@ using namespace mpfr;
 
 ostream& mpreal_output10base(ostream& out, const string& fmt, const mpreal& value);
 ostream& mpreal_outputNbase(ostream& out, int base, const mpreal& value);
+
+#endif
diff --git a/src/object.hpp b/src/object.hpp
index 994e1ab..723c5f0 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -1,5 +1,5 @@
-#ifndef OBJECT_HPP
-#define OBJECT_HPP
+#ifndef OBJECT_HPP_
+#define OBJECT_HPP_
 
 #define MPFR_USE_NO_MACRO
 #include <mpfr.h>
diff --git a/src/program.hpp b/src/program.hpp
index 02b5eb9..9a1cef4 100644
--- a/src/program.hpp
+++ b/src/program.hpp
@@ -1,5 +1,5 @@
-#ifndef PROGRAM_HPP
-#define PROGRAM_HPP
+#ifndef PROGRAM_HPP_
+#define PROGRAM_HPP_
 
 // std c++
 #include <fstream>
diff --git a/src/stack.hpp b/src/stack.hpp
index 8e30ebb..237e808 100644
--- a/src/stack.hpp
+++ b/src/stack.hpp
@@ -1,5 +1,5 @@
-#ifndef __stack_h__
-#define __stack_h__
+#ifndef STACK_HPP_
+#define STACK_HPP_
 
 #include <string.h>
 
diff --git a/src/version.h b/src/version.h
index 52d5a96..7af9ae7 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1,2 +1,7 @@
+#ifndef VERSION_H_
+#define VERSION_H_
+
 #define RPN_VERSION "2.4"
 #define RPN_UNAME "rpn v" RPN_VERSION ", (c) 2017 <louis@rubet.fr>, GNU LGPL v3"
+
+#endif