diff --git a/configure.ac b/configure.ac
index 66c8cbe..3f546e9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -475,7 +475,8 @@ AC_LINK_IFELSE(
     {
       stdbuf = 1;
     }]],[[
-    return !(stdbuf == 1);]])
+    if (stdbuf != 1)
+      return 1;]])
   ],
   [stdbuf_supported=yes])
 AC_MSG_RESULT([$stdbuf_supported])