diff --git a/configure.in b/configure.in
index 7585ced..d9bfa9f 100644
--- a/configure.in
+++ b/configure.in
@@ -53,6 +53,7 @@
 dnl Add these flags if we're using GCC.
 case "$GCC" in
  yes)
+   CFLAGS="$CFLAGS -W"
    CFLAGS="$CFLAGS -Wall"
    CFLAGS="$CFLAGS -Wshadow"
    CFLAGS="$CFLAGS -Wcast-qual"