diff --git a/quickjs.c b/quickjs.c
index 2824637..459eb08 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -6529,7 +6529,7 @@ static void build_backtrace(JSContext *ctx, JSValue error_obj,
                 line_num1 = find_line_num(ctx, b,
                                           sf->cur_pc - b->byte_code_buf - 1,
                                           &col_num1);
-                atom_str = JS_AtomToCString(ctx, b->filename);
+                atom_str = b->filename ? JS_AtomToCString(ctx, b->filename) : NULL;
                 dbuf_printf(&dbuf, " (%s", atom_str ? atom_str : "<null>");
                 JS_FreeCString(ctx, atom_str);
                 if (line_num1 != -1)