Index: GNUmakefile
--- GNUmakefile.orig
+++ GNUmakefile
@@ -1212,7 +1212,7 @@ endif
 
 #### Includes
 
-COMPILERFLAGS += \
+COMPILERFLAGS := \
     -I$(engine_inc) \
     -I$(mact_inc) \
     -I$(audiolib_inc) \
@@ -1223,6 +1223,7 @@ COMPILERFLAGS += \
     -I$(libsmackerdec_inc) \
     -I$(hmpplay_inc) \
     -MP -MMD \
+    $(COMPILERFLAGS)
 
 ifneq (0,$(USE_PHYSFS))
     COMPILERFLAGS += -I$(physfs_inc) -DUSE_PHYSFS
