diff --git a/Makefile.os2 b/Makefile.os2
index 89985e67c..40ba0e8fc 100644
--- a/Makefile.os2
+++ b/Makefile.os2
@@ -63,9 +63,9 @@ CFLAGS_DLL+= -DHAVE_LIBUSB_H=1
 # building SDL itself (for DECLSPEC):
 CFLAGS_DLL+= -DBUILD_SDL
 
-CFLAGS+= -DSDL_BUILD_MAJOR_VERSION=$(MAJOR_VERSION)
-CFLAGS+= -DSDL_BUILD_MINOR_VERSION=$(MINOR_VERSION)
-CFLAGS+= -DSDL_BUILD_MICRO_VERSION=$(MICRO_VERSION)
+CFLAGS_DLL+= -DSDL_BUILD_MAJOR_VERSION=$(MAJOR_VERSION)
+CFLAGS_DLL+= -DSDL_BUILD_MINOR_VERSION=$(MINOR_VERSION)
+CFLAGS_DLL+= -DSDL_BUILD_MICRO_VERSION=$(MICRO_VERSION)
 
 SRCS = SDL.c SDL_assert.c SDL_error.c SDL_log.c SDL_dataqueue.c SDL_hints.c SDL_list.c
 SRCS+= SDL_getenv.c SDL_iconv.c SDL_malloc.c SDL_qsort.c SDL_stdlib.c SDL_string.c SDL_strtokr.c SDL_crc32.c