diff --git a/acinclude.m4 b/acinclude.m4
index f32e86cda5..355ee3a61c 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -2158,7 +2158,7 @@ AC_DEFUN([CURL_VERIFY_RUNTIMELIBS], [
     dnl point also is available run-time!
     AC_MSG_CHECKING([run-time libs availability])
     CURL_RUN_IFELSE([
-main()
+int main()
 {
   return 0;
 }
diff --git a/configure.ac b/configure.ac
index 18b7ae0f1b..ff8f5df9b9 100755
--- a/configure.ac
+++ b/configure.ac
@@ -61,6 +61,13 @@ AC_SUBST(CONFIGURE_OPTIONS)
 CURL_CFLAG_EXTRAS=""
 if test X"$want_werror" = Xyes; then
   CURL_CFLAG_EXTRAS="-Werror"
+  if test "$compiler_id" = "GNU_C"; then
+    dnl enable -pedantic-errors for GCC 5 and later,
+    dnl as before that it was the same as -Werror=pedantic
+    if test "$compiler_num" -ge "500"; then
+      CURL_CFLAG_EXTRAS="$CURL_CFLAG_EXTRAS -pedantic-errors"
+    fi
+  fi
 fi
 AC_SUBST(CURL_CFLAG_EXTRAS)