--- a/make/autoconf/flags-cflags.m4
+++ b/make/autoconf/flags-cflags.m4
@@ -747,6 +747,9 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_CPU_DEP],
       fi
     elif test "x$FLAGS_CPU" = xs390x; then
       $1_CFLAGS_CPU="-mbackchain -march=z10"
+      if test "x$VENDOR_FLAGS_CPU" != x; then
+        $1_CFLAGS_CPU="-mbackchain $VENDOR_FLAGS_CPU"
+      fi
     fi
 
     if test "x$FLAGS_CPU_ARCH" != xarm &&  test "x$FLAGS_CPU_ARCH" != xppc; then