diff --git a/Makefile b/Makefile
index b86c214d76..e58bc87768 100644
--- a/Makefile
+++ b/Makefile
@@ -241,7 +241,7 @@ ifeq ($(AST_DEVMODE),yes)
 endif
 
 ifneq ($(findstring BSD,$(OSARCH)),)
-  _ASTCFLAGS+=-I/usr/local/include
+  _ASTCFLAGS+=-isystem /usr/local/include
 endif
 
 ifeq ($(findstring -march,$(_ASTCFLAGS) $(ASTCFLAGS)),)