diff --git a/configure.ac b/configure.ac
index dcb8aa0..7d7ab76 100644
--- a/configure.ac
+++ b/configure.ac
@@ -796,7 +796,7 @@ fi
 
 AC_SUBST(SOCAT_USE_COMPRESS)
 
-if man --help | grep -q -e --warnings
+if man --help |& grep -q -e --warnings
 then
   MAN_HAS_WARNINGS=1
 else