diff --git a/configure.in b/configure.in
index ea23bf901f3f499e12972f1e3d57239a2bc62f57..ba7d0c3d64d1fded9934298db8c2461fe034c4fd 100644
--- a/configure.in
+++ b/configure.in
@@ -69,7 +69,7 @@ AC_ARG_ENABLE(debug,
   *)   AC_MSG_RESULT(yes)
 
     CPPFLAGS="$CPPFLAGS -DMALLOCDEBUG"
-    CFLAGS="-W -Wall -Wwrite-strings -pedantic -g" 
+    CFLAGS="-W -Wall -Wwrite-strings -pedantic -Wundef -Wpointer-arith -Wcast-align -Wnested-externs -g" 
        ;;
   esac ],
        AC_MSG_RESULT(no)