diff --git a/ares/Makefile.vc6 b/ares/Makefile.vc6
index eb064b910c..84352dbe59 100644
--- a/ares/Makefile.vc6
+++ b/ares/Makefile.vc6
@@ -43,7 +43,7 @@ CFLAGS  = $(CFLAGS) -O2 -Og
 LDFLAGS = $(LDFLAGS) -release
 !endif
 
-CFLAGS  = -I.\.
+CFLAGS  = $(CFLAGS) -I.\.
 
 OBJECTS = $(OBJ_DIR)\ares_fds.obj              \
           $(OBJ_DIR)\ares_process.obj          \