diff --git a/quickjs.c b/quickjs.c
index bbfea93..8fcf5ba 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -50598,6 +50598,8 @@ static JSValue js_debugger_find_closure_var(JSStackFrame *sf, JSClosureVar *cvar
                 return sf->var_buf[cvar->var_idx];
         }
 
+        if (!b->closure_var)
+            break;
         cvar = b->closure_var + cvar->var_idx;
     }