--- src/Makefile
+++ src/Makefile
@@ -1,7 +1,7 @@
 # Makefile for ptpd
 
 RM = rm -f
-CFLAGS = -Wall
+CFLAGS += -Wall
 #CPPFLAGS = -DPTPD_DBG -DPTPD_NO_DAEMON
 
 PROG = ptpd