diff --git a/makefile b/makefile
index f04d95d4d98..df4ff31b5a2 100644
--- a/makefile
+++ b/makefile
@@ -83,7 +83,9 @@ endif
 ifeq ($(firstword $(filter FreeBSD,$(UNAME))),FreeBSD)
 TARGETOS = freebsd
 endif
-
+ifeq ($(firstword $(filter OpenBSD,$(UNAME))),FreeBSD)
+TARGETOS = openbsd
+endif
 ifeq ($(firstword $(filter Darwin,$(UNAME))),Darwin)
 TARGETOS = macosx
 endif
@@ -97,6 +99,9 @@ ifndef PTR64
 ifeq ($(firstword $(filter x86_64,$(UNAME))),x86_64)
 PTR64 = 1
 endif
+ifeq ($(firstword $(filter amd64,$(UNAME))),amd64)
+PTR64 = 1
+endif
 endif
 
 # Autodetect BIGENDIAN 
diff --git a/src/osd/sdl/sdl.mak b/src/osd/sdl/sdl.mak
index 81d14693ab8..2eabc519abf 100644
--- a/src/osd/sdl/sdl.mak
+++ b/src/osd/sdl/sdl.mak
@@ -315,10 +315,12 @@ CFLAGS += -Upowerpc
 SUPPORTSM32M64 = 1
 endif
 
+ifneq (,$(findstring amd64,$(UNAME)))
+SUPPORTSM32M64 = 1
+endif
 ifneq (,$(findstring x86_64,$(UNAME)))
 SUPPORTSM32M64 = 1
 endif
-
 ifneq (,$(findstring i386,$(UNAME)))
 SUPPORTSM32M64 = 1
 endif
diff --git a/src/osd/sdl/sdlprefix.h b/src/osd/sdl/sdlprefix.h
index 0fc1ab6be8c..aed6f845421 100644
--- a/src/osd/sdl/sdlprefix.h
+++ b/src/osd/sdl/sdlprefix.h
@@ -33,12 +33,10 @@
 #undef _XPG5
 #undef _XPG4_2
 
-#if 1
 #undef _XOPEN_SOURCE
 #undef _XOPEN_VERSION
 #define _XOPEN_SOURCE
 #define _XOPEN_VERSION 4
-#endif
 
 #elif defined(__irix__) || defined(__sgi)
 #define SDLMAME_IRIX 1