diff --git a/redoconf/configure.sh b/redoconf/configure.sh
index 38986e9..0160493 100644
--- a/redoconf/configure.sh
+++ b/redoconf/configure.sh
@@ -196,7 +196,7 @@ done >>_flags.tmp
 # unnecessary rebuilds.  redo-stamp can do this for a redo target,
 # but _flags is being generated by this configure script, which is
 # not a redo target.
-if [ -e _flags ] && cmp _flags.tmp _flags >/dev/null; then
+if [ -e _flags ] && cmp -s _flags.tmp _flags; then
 	rm -f _flags.tmp
 else
 	rm -f _flags