diff --git a/configure.sh b/configure.sh
--- a/configure.sh
+++ b/configure.sh
@@ -70,10 +70,10 @@ done
 
 [ X"$CC" = X ] && CC=gcc
 
-if [ X"$CFLAGS" = X ]
+if [ TRUE ]
 then
   [ $debug = unknown ] && debug=no
-  CFLAGS="-W -Wall -Wextra -Wredundant-decls -std=gnu99"
+  CFLAGS="$CFLAGS -W -Wall -Wextra -Wredundant-decls -std=gnu99"
   [ $static = yes ] && CFLAGS="$CFLAGS -static"
   [ $shared = yes ] && CFLAGS="$CFLAGS -fPIC"
   [ $flags = none ] || CFLAGS="$CFLAGS $flags"