diff --git a/config.lib b/config.lib
index 565fd46b85..943f5a6f16 100644
--- a/config.lib
+++ b/config.lib
@@ -1205,7 +1205,8 @@ make_cflags_and_ldflags() {
 
 	if [ -n "$sdl_config" ]; then
 		CFLAGS="$CFLAGS -DWITH_SDL"
-		CFLAGS="$CFLAGS `$sdl_config --cflags`"
+		# SDL must not add _GNU_SOURCE as it breaks many platforms
+		CFLAGS="$CFLAGS `$sdl_config --cflags | sed 's~-D_GNU_SOURCE[^ ]*~~'`"
 		if [ "$os" != "MINGW" ] && [ "$os" != "CYGWIN" ] && [ "$os" != "WINCE" ]; then
 			if [ "$enable_static" != "0" ]; then
 				LIBS="$LIBS `$sdl_config --static-libs`"
diff --git a/src/stdafx.h b/src/stdafx.h
index 99595ffd74..97785e0bec 100644
--- a/src/stdafx.h
+++ b/src/stdafx.h
@@ -145,11 +145,6 @@
 	#include <malloc.h> // alloca()
 #endif
 
-#if defined(__MINGW32__) && defined(_GNU_SOURCE)
-	/* For some weird reasons, SDL defines _GNU_SOURCE */
-	#undef _GNU_SOURCE
-#endif
-
 #if defined(WIN32)
 	#define WIN32_LEAN_AND_MEAN     // Exclude rarely-used stuff from Windows headers
 #endif