diff --git a/acinclude.m4 b/acinclude.m4
index 436adb60543328f2406a8be1126d0a207202dd30..790248b080da0c3a4e46d351f0db6e664d40de28 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -120,7 +120,7 @@ AC_DEFUN([CURL_CHECK_LIB_XNET], [
     AC_LANG_SOURCE([[
 int main (void)
 {
-#if defined(__hpux) && defined(_XOPEN_SOURCE) && defined(_XOPEN_SOURCE >= 600)
+#if defined(__hpux) && defined(_XOPEN_SOURCE) && (_XOPEN_SOURCE >= 600)
   return 0;
 #elif defined(__hpux) && defined(_XOPEN_SOURCE_EXTENDED)
   return 0;
diff --git a/ares/acinclude.m4 b/ares/acinclude.m4
index 6b02776f6b16f607906cbe47a9764eab56143721..e9690a71307f227431d51496865ab14c2c2cc20c 100644
--- a/ares/acinclude.m4
+++ b/ares/acinclude.m4
@@ -98,7 +98,7 @@ AC_DEFUN([CARES_CHECK_LIB_XNET], [
     AC_LANG_SOURCE([[
 int main (void)
 {
-#if defined(__hpux) && defined(_XOPEN_SOURCE) && defined(_XOPEN_SOURCE >= 600)
+#if defined(__hpux) && defined(_XOPEN_SOURCE) && (_XOPEN_SOURCE >= 600)
   return 0;
 #elif defined(__hpux) && defined(_XOPEN_SOURCE_EXTENDED)
   return 0;