diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrFunctionFactory.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrFunctionFactory.kt
index d227543c509..dd2bae03b47 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrFunctionFactory.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/descriptors/IrFunctionFactory.kt
@@ -93,7 +93,7 @@ class IrFunctionFactory(private val irBuiltIns: IrBuiltIns, private val symbolTa
     override fun functionN(arity: Int, declarator: SymbolTable.((IrClassSymbol) -> IrClass) -> IrClass): IrClass {
         return functionNMap.getOrPut(arity) {
             symbolTable.declarator { symbol ->
-                val descriptor = symbol.descriptor as FunctionClassDescriptor
+                val descriptor = symbol.descriptor
                 val descriptorFactory = FunctionDescriptorFactory.RealDescriptorFactory(descriptor, symbolTable)
                 createFunctionClass(symbol, false, false, arity, irBuiltIns.functionClass, kotlinPackageFragment, descriptorFactory)
             }
@@ -159,7 +159,7 @@ class IrFunctionFactory(private val irBuiltIns: IrBuiltIns, private val symbolTa
         abstract fun classReceiverParameterDescriptor(): ReceiverParameterDescriptor
         abstract fun FunctionDescriptor.memberReceiverParameterDescriptor(): ReceiverParameterDescriptor
 
-        class RealDescriptorFactory(private val classDescriptor: FunctionClassDescriptor, symbolTable: SymbolTable) :
+        class RealDescriptorFactory(private val classDescriptor: ClassDescriptor, symbolTable: SymbolTable) :
             FunctionDescriptorFactory(symbolTable) {
             override fun memberDescriptor(name: String, factory: (IrSimpleFunctionSymbol) -> IrSimpleFunction): IrSimpleFunctionSymbol {
                 val descriptor = classDescriptor.unsubstitutedMemberScope.run {
@@ -439,6 +439,7 @@ class IrFunctionFactory(private val irBuiltIns: IrBuiltIns, private val symbolTa
         descriptorFactory: FunctionDescriptorFactory
     ): IrClass {
         val name = functionClassName(isK, isSuspend, n)
+        if (symbol.isBound) return symbol.owner
         val klass = IrClassImpl(
             offset, offset, classOrigin, symbol, Name.identifier(name), ClassKind.INTERFACE, Visibilities.PUBLIC, Modality.ABSTRACT
         )
diff --git a/compiler/testData/codegen/box/funInterface/nonAbstractMethod.kt b/compiler/testData/codegen/box/funInterface/nonAbstractMethod.kt
index 2b5a188c64a..b77615ddd35 100644
--- a/compiler/testData/codegen/box/funInterface/nonAbstractMethod.kt
+++ b/compiler/testData/codegen/box/funInterface/nonAbstractMethod.kt
@@ -1,5 +1,4 @@
 // IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND_FIR: JVM_IR
 
 interface I {
     fun inherited(s: String): String = privateInherited(s)
diff --git a/compiler/testData/codegen/box/javaInterop/notNullAssertions/functionAssertion.kt b/compiler/testData/codegen/box/javaInterop/notNullAssertions/functionAssertion.kt
index 7749511e5f6..3dee7701f44 100644
--- a/compiler/testData/codegen/box/javaInterop/notNullAssertions/functionAssertion.kt
+++ b/compiler/testData/codegen/box/javaInterop/notNullAssertions/functionAssertion.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // SKIP_JDK6
 // TARGET_BACKEND: JVM
 // FILE: F.java
diff --git a/compiler/testData/codegen/box/jvm8/defaults/allCompatibility/funInterface.kt b/compiler/testData/codegen/box/jvm8/defaults/allCompatibility/funInterface.kt
index 07ab0d8e77c..2bfcccf6100 100644
--- a/compiler/testData/codegen/box/jvm8/defaults/allCompatibility/funInterface.kt
+++ b/compiler/testData/codegen/box/jvm8/defaults/allCompatibility/funInterface.kt
@@ -1,6 +1,5 @@
 // !JVM_DEFAULT_MODE: all-compatibility
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
 // JVM_TARGET: 1.8
 // WITH_RUNTIME
 
diff --git a/compiler/testData/codegen/box/jvm8/defaults/noDefaultImpls/funInterface.kt b/compiler/testData/codegen/box/jvm8/defaults/noDefaultImpls/funInterface.kt
index 1f4bb55a435..13d03169501 100644
--- a/compiler/testData/codegen/box/jvm8/defaults/noDefaultImpls/funInterface.kt
+++ b/compiler/testData/codegen/box/jvm8/defaults/noDefaultImpls/funInterface.kt
@@ -1,6 +1,5 @@
 // !JVM_DEFAULT_MODE: all
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
 // JVM_TARGET: 1.8
 // WITH_RUNTIME
 
diff --git a/compiler/testData/codegen/box/sam/constructors/nonLiteralFilenameFilter.kt b/compiler/testData/codegen/box/sam/constructors/nonLiteralFilenameFilter.kt
index e975af5d038..362479fb553 100644
--- a/compiler/testData/codegen/box/sam/constructors/nonLiteralFilenameFilter.kt
+++ b/compiler/testData/codegen/box/sam/constructors/nonLiteralFilenameFilter.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // TARGET_BACKEND: JVM
 
 import java.io.*
diff --git a/compiler/testData/codegen/box/sam/predicateSamWrapper.kt b/compiler/testData/codegen/box/sam/predicateSamWrapper.kt
index 102fe13141b..ef7dc3f32ff 100644
--- a/compiler/testData/codegen/box/sam/predicateSamWrapper.kt
+++ b/compiler/testData/codegen/box/sam/predicateSamWrapper.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // TARGET_BACKEND: JVM
 // WITH_RUNTIME
 // FULL_JDK