diff --git a/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.jet b/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.jet
new file mode 100644
index 00000000000..b9d90ddbb5f
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.jet
@@ -0,0 +1,27 @@
+//KT-1821 Write test for ITERATOR_AMBIGUITY diagnostic
+
+trait MyCollectionInterface {
+}
+
+trait MyAnotherCollectionInterface {
+}
+
+class MyCollection : MyCollectionInterface, MyAnotherCollectionInterface {
+}
+
+fun MyCollectionInterface.iterator() = MyIterator()
+
+fun MyAnotherCollectionInterface.iterator() = MyIterator()
+
+class MyIterator {
+    fun next() : MyElement = MyElement()
+    fun hasNext() = true
+}
+
+class MyElement
+
+fun test1(collection: MyCollection) {
+    collection.<!OVERLOAD_RESOLUTION_AMBIGUITY!>iterator()<!>
+    for (val element in <!ITERATOR_AMBIGUITY!>collection<!>) {
+    }
+}
\ No newline at end of file