diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/RangeCodegenUtil.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/RangeCodegenUtil.kt
index 9591da0b726..076dbedc7f0 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/RangeCodegenUtil.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/RangeCodegenUtil.kt
@@ -254,3 +254,9 @@ fun getAsmRangeElementTypeForPrimitiveRangeOrProgression(rangeCallee: CallableDe
 
     throw AssertionError("Unexpected range type: $rangeType")
 }
+
+fun isCharSequenceIterator(descriptor: CallableDescriptor) =
+    descriptor.isTopLevelExtensionOnType("iterator", "kotlin.text") {
+        it.constructor.declarationDescriptor?.isTopLevelInPackage("CharSequence", "kotlin")
+                ?: false
+    }
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/range/RangeValues.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/range/RangeValues.kt
index b799221a8a8..d044f3c92dd 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/range/RangeValues.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/range/RangeValues.kt
@@ -47,6 +47,8 @@ fun ExpressionCodegen.createRangeValueForExpression(rangeExpression: KtExpressio
     val rangeType = bindingContext.getType(rangeExpression)!!
     val asmRangeType = asmType(rangeType)
 
+    val loopRangeIteratorResolvedCall = bindingContext[BindingContext.LOOP_RANGE_ITERATOR_RESOLVED_CALL, rangeExpression]
+
     val builtIns = state.module.builtIns
     return when {
         asmRangeType.sort == Type.ARRAY -> {
@@ -62,9 +64,9 @@ fun ExpressionCodegen.createRangeValueForExpression(rangeExpression: KtExpressio
             PrimitiveRangeRangeValue(rangeExpression)
         isPrimitiveProgression(rangeType) ->
             PrimitiveProgressionRangeValue(rangeExpression)
-        isSubtypeOfString(rangeType, builtIns) ->
+        isSubtypeOfString(rangeType, builtIns) && isCharSequenceIteratorCall(loopRangeIteratorResolvedCall) ->
             CharSequenceRangeValue(true, AsmTypes.JAVA_STRING_TYPE)
-        isSubtypeOfCharSequence(rangeType, builtIns) ->
+        isSubtypeOfCharSequence(rangeType, builtIns) && isCharSequenceIteratorCall(loopRangeIteratorResolvedCall) ->
             CharSequenceRangeValue(false, null)
         else ->
             IterableRangeValue()
@@ -147,4 +149,7 @@ private fun ExpressionCodegen.createReversedRangeValueOrNull(rangeCall: Resolved
     val receiver = rangeCall.extensionReceiver as? ExpressionReceiver ?: return null
     val receiverRangeValue = createRangeValueForExpression(receiver.expression) as? ReversableRangeValue ?: return null
     return ReversedRangeValue(receiverRangeValue)
-}
\ No newline at end of file
+}
+
+private fun isCharSequenceIteratorCall(iteratorCall: ResolvedCall<*>?) =
+    iteratorCall?.resultingDescriptor?.let { isCharSequenceIterator(it) } ?: false
\ No newline at end of file
diff --git a/compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt b/compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt
new file mode 100644
index 00000000000..e7853e62294
--- /dev/null
+++ b/compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt
@@ -0,0 +1,25 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+
+operator fun String.iterator(): IntIterator = object : IntIterator() {
+    private var index = 0
+
+    override fun nextInt() = codePointAt(index).apply {
+        index += Character.charCount(this)
+    }
+
+    override fun hasNext(): Boolean = index < length
+}
+
+fun String.collectInts(): List<Int> {
+    val result = ArrayList<Int>()
+    for (c in this) {
+        result.add(c)
+    }
+    return result
+}
+
+fun box(): String {
+    val ints = String(Character.toChars(127849)).collectInts()
+    return if (ints == listOf(127849)) "OK" else "Fail: $ints"
+}
\ No newline at end of file
diff --git a/compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java b/compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
index 08216ff9454..a04ff4b57f1 100644
--- a/compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
+++ b/compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java
@@ -15480,6 +15480,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/ranges/forInStringVarUpdatedInLoopBody.kt");
         }
 
+        @TestMetadata("forInStringWithCustomIterator.kt")
+        public void testForInStringWithCustomIterator() throws Exception {
+            runTest("compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt");
+        }
+
         @TestMetadata("forIntRange.kt")
         public void testForIntRange() throws Exception {
             runTest("compiler/testData/codegen/box/ranges/forIntRange.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
index 1de808e96fe..d2509d196f8 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java
@@ -15480,6 +15480,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/ranges/forInStringVarUpdatedInLoopBody.kt");
         }
 
+        @TestMetadata("forInStringWithCustomIterator.kt")
+        public void testForInStringWithCustomIterator() throws Exception {
+            runTest("compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt");
+        }
+
         @TestMetadata("forIntRange.kt")
         public void testForIntRange() throws Exception {
             runTest("compiler/testData/codegen/box/ranges/forIntRange.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
index 20d495db09f..a3dea99c68a 100644
--- a/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java
@@ -15480,6 +15480,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/ranges/forInStringVarUpdatedInLoopBody.kt");
         }
 
+        @TestMetadata("forInStringWithCustomIterator.kt")
+        public void testForInStringWithCustomIterator() throws Exception {
+            runTest("compiler/testData/codegen/box/ranges/forInStringWithCustomIterator.kt");
+        }
+
         @TestMetadata("forIntRange.kt")
         public void testForIntRange() throws Exception {
             runTest("compiler/testData/codegen/box/ranges/forIntRange.kt");