diff --git a/GNUmakefile.llvm b/GNUmakefile.llvm
index cc28695d2485b7bac8c5b07a8bf394dda42bc288..d048e32174638e76304232a0f4d8e4d95f1f17fe 100644
--- a/GNUmakefile.llvm
+++ b/GNUmakefile.llvm
@@ -288,13 +288,13 @@ ifeq "$(shell echo '$(HASH)include <sys/ipc.h>@$(HASH)include <sys/shm.h>@int ma
         SHMAT_OK=1
 else
         SHMAT_OK=0
-        #CFLAGS+=-DUSEMMAP=1
+        CFLAGS_SAFE+=-DUSEMMAP=1
         LDFLAGS += -Wno-deprecated-declarations
 endif
 
 ifeq "$(TEST_MMAP)" "1"
         SHMAT_OK=0
-        CFLAGS+=-DUSEMMAP=1
+        CFLAGS_SAFE+=-DUSEMMAP=1
         LDFLAGS += -Wno-deprecated-declarations
 endif