diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt
index 78915ba888a..e9edba8397b 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt
@@ -70,7 +70,14 @@ class DelegationResolver<T : CallableMemberDescriptor> private constructor(
             getDelegatableMembers(delegatedInterfaceType).map { memberDescriptor ->
                 val newModality = if (memberDescriptor.modality == Modality.ABSTRACT) Modality.OPEN else memberDescriptor.modality
                 @Suppress("UNCHECKED_CAST")
-                (memberDescriptor.copy(ownerDescriptor, newModality, Visibilities.INHERITED, DELEGATION, false) as T)
+                memberDescriptor.newCopyBuilder()
+                        .setOwner(ownerDescriptor)
+                        .setDispatchReceiverParameter(ownerDescriptor.thisAsReceiverParameter)
+                        .setModality(newModality)
+                        .setVisibility(Visibilities.INHERITED)
+                        .setKind(DELEGATION)
+                        .setCopyOverrides(false)
+                        .build() as T
             }
 
     private fun checkClashWithOtherDelegatedMember(candidate: T, delegatedMembers: Collection<T>): Boolean {
diff --git a/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt b/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt
index 08d09eb2d9e..223c7f8d629 100644
--- a/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt
+++ b/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt
@@ -168,13 +168,14 @@ class ClassGenerator(val declarationGenerator: DeclarationGenerator) : Generator
     private fun generateDelegateFunctionBody(irDelegate: IrFieldImpl, delegated: FunctionDescriptor, overridden: FunctionDescriptor): IrBlockBodyImpl {
         val startOffset = irDelegate.startOffset
         val endOffset = irDelegate.endOffset
-        val classOwner = delegated.containingDeclaration.assertedCast<ClassDescriptor> { "Class member expected: $delegated" }
+        val dispatchReceiver = delegated.dispatchReceiverParameter ?:
+                               throw AssertionError("Delegated member should have a dispatch receiver: $delegated")
 
         val irBlockBody = IrBlockBodyImpl(startOffset, endOffset)
         val returnType = overridden.returnType!!
         val irCall = IrCallImpl(startOffset, endOffset, returnType, overridden, null)
         irCall.dispatchReceiver = IrGetFieldImpl(startOffset, endOffset, irDelegate.descriptor,
-                                                 IrGetValueImpl(startOffset, endOffset, classOwner.thisAsReceiverParameter)
+                                                 IrGetValueImpl(startOffset, endOffset, dispatchReceiver)
                                                  )
         irCall.extensionReceiver = delegated.extensionReceiverParameter?.let { extensionReceiver ->
             IrGetValueImpl(startOffset, endOffset, extensionReceiver)