--- a/configure
+++ b/configure
@@ -19631,7 +19631,7 @@
 	CFLAGS="-O2 -Wall -Wwrite-strings \
 		-Wpointer-arith -Wcast-qual -Wcast-align \
 		-Wstrict-prototypes -Wmissing-prototypes \
-		-Wnested-externs -Winline -Wshadow"
+		-Wnested-externs -Winline -Wshadow $CFLAGS"
 fi
 
 # Checks for libraries.
