diff --git a/tccgen.c b/tccgen.c
index bc9b24f..4baa5ff 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -3169,6 +3169,8 @@ static void post_type(CType *type, AttributeDef *ad)
                 n = vtop->c.i;
                 if (n < 0)
                     error("invalid array size");
+            } else if (!local_stack) {
+                error("expected constant expression (variably modified array at file scope)");
             } else {
                 if (!is_integer_btype(vtop->type.t & VT_BTYPE))
                     error("size of variable length array should be an integer");