diff --git a/lib/db/level.js b/lib/db/level.js
index 3a93b6c2..d4cb8008 100644
--- a/lib/db/level.js
+++ b/lib/db/level.js
@@ -144,6 +144,8 @@ Iterator.prototype.seek = function seek(key) {
 };
 
 Iterator.prototype.end = function end(callback) {
+  if (this._end)
+    return callback(new Error('end() already called on iterator.'));
   this._end = true;
   this.iter.end(callback);
 };