diff --git a/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/indy/LambdaMetafactoryArguments.kt b/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/indy/LambdaMetafactoryArguments.kt
index df640b459e8..fb57d90f06b 100644
--- a/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/indy/LambdaMetafactoryArguments.kt
+++ b/compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/indy/LambdaMetafactoryArguments.kt
@@ -60,10 +60,6 @@ internal sealed class MetafactoryArgumentsResult {
         // TODO make sure indy and Kotlin bytecode inliner work well together
         object InliningHazard : Failure()
 
-        // Resulting object should be Serializable.
-        // TODO implement serialization support required by j.l.invoke.LambdaMetafactory
-        object SerializationHazard : Failure()
-
         // There's something special about a function we are referencing.
         // Wrapping it into a proxy local function might help.
         object FunctionHazard : Failure()
@@ -549,7 +545,9 @@ internal class LambdaMetafactoryArgumentsBuilder(
         )
     }
 
-    private fun computeParameterTypeAdaptationConstraint(adapteeType: IrType, expectedType: IrType): TypeAdaptationConstraint? {
+    private fun computeParameterTypeAdaptationConstraint(adapteeType0: IrType, expectedType0: IrType): TypeAdaptationConstraint? {
+        val adapteeType = adapteeType0.unwrapDefinitelyNotNullType()
+        val expectedType = expectedType0.unwrapDefinitelyNotNullType()
         if (adapteeType !is IrSimpleType)
             throw AssertionError("Simple type expected: ${adapteeType.render()}")
         if (expectedType !is IrSimpleType)
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrBasedDescriptors.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrBasedDescriptors.kt
index 8d73ba75cb5..d249723a9b2 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrBasedDescriptors.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrBasedDescriptors.kt
@@ -1134,11 +1134,13 @@ private fun getContainingDeclaration(declaration: IrDeclaration): DeclarationDes
 fun IrType.toIrBasedKotlinType(): KotlinType = when (this) {
     is IrSimpleType ->
         makeKotlinType(classifier, arguments, hasQuestionMark)
-    is IrDefinitelyNotNullType ->
-        DefinitelyNotNullType.makeDefinitelyNotNull(this.original.toIrBasedKotlinType().unwrap())
-            ?: throw AssertionError("Can't reconstruct a definitely not-null type: ${this.render()}")
+    is IrDefinitelyNotNullType -> {
+        val kotlinType = this.original.toIrBasedKotlinType()
+        DefinitelyNotNullType.makeDefinitelyNotNull(kotlinType.unwrap())
+            ?: kotlinType
+    }
     else ->
-        TODO(toString())
+        throw AssertionError("Unexpected type: $this = ${this.render()}")
 }
 
 private fun makeKotlinType(
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeUtils.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeUtils.kt
index 1c12671a0ed..9916e8ae419 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeUtils.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeUtils.kt
@@ -70,3 +70,9 @@ fun IrType.toArrayOrPrimitiveArrayType(irBuiltIns: IrBuiltIns): IrType =
     } else {
         irBuiltIns.arrayClass.typeWith(this)
     }
+
+fun IrType.unwrapDefinitelyNotNullType(): IrType =
+    if (this is IrDefinitelyNotNullType)
+        this.original.unwrapDefinitelyNotNullType()
+    else
+        this