diff --git a/build/premake/src/Src/gnu_cpp.c b/build/premake/src/Src/gnu_cpp.c
index 1c6a6d3149..a6033387e3 100644
--- a/build/premake/src/Src/gnu_cpp.c
+++ b/build/premake/src/Src/gnu_cpp.c
@@ -522,9 +522,9 @@ static const char* listCppTargets(const char* name)
 				if (os_is("windows"))
 					opts = "";
 				else if (os_is("macosx"))
-					opts = "-dOS_UNIX=1 ";
+					opts = "-D OS_UNIX=1 ";
 				else
-					opts = "-dDONT_USE_UNDERLINE=1 -dOS_UNIX=1 ";
+					opts = "-D DONT_USE_UNDERLINE=1 -D OS_UNIX=1 ";
 				
 				strcat(g_buffer, "nasm "); strcat(g_buffer, opts); 
 				strcat(g_buffer, " -i"); strcat(g_buffer,input_dir );