diff --git a/lib/core.js b/lib/core.js
index 1d6ce0c869f..38aac50d48f 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -278,7 +278,7 @@ declare class Symbol {
    * by Array.prototype.concat.
    */
   static isConcatSpreadable: $SymboIsConcatSpreadable;
-  static iterator: string; // polyfill '@@iterator'
+  static iterator: '@@iterator'; // polyfill '@@iterator'
   /**
    * Returns a key from the global symbol registry matching the given Symbol if found.
    * Otherwise, returns a undefined.
diff --git a/tests/symbol/iterator.js b/tests/symbol/iterator.js
new file mode 100644
index 00000000000..03a8ee49423
--- /dev/null
+++ b/tests/symbol/iterator.js
@@ -0,0 +1,6 @@
+declare var foo: {
+  @@iterator: Iterator<number>,
+};
+
+(foo[Symbol.iterator]: Iterator<number>); // OK
+(foo[Symbol.iterator]: boolean); // Error
diff --git a/tests/symbol/symbol.exp b/tests/symbol/symbol.exp
index c5bf86e192c..99a71bc7e6c 100644
--- a/tests/symbol/symbol.exp
+++ b/tests/symbol/symbol.exp
@@ -1,3 +1,21 @@
+Error -------------------------------------------------------------------------------------------------- iterator.js:6:2
+
+Cannot cast `foo[Symbol.iterator]` to boolean because `$Iterator` [1] is incompatible with boolean [2].
+[incompatible-cast]
+
+   iterator.js:6:2
+   6| (foo[Symbol.iterator]: boolean); // Error
+       ^^^^^^^^^^^^^^^^^^^^
+
+References:
+   iterator.js:2:15
+   2|   @@iterator: Iterator<number>,
+                    ^^^^^^^^^^^^^^^^ [1]
+   iterator.js:6:24
+   6| (foo[Symbol.iterator]: boolean); // Error
+                             ^^^^^^^ [2]
+
+
 Error --------------------------------------------------------------------------------------------------- symbol.js:8:17
 
 Cannot call `Symbol` because no more than 1 argument is expected by function type [1]. [extra-arg]
@@ -137,4 +155,4 @@ References:
 
 
 
-Found 8 errors
+Found 9 errors