diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/FakeOverrideGenerator.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/FakeOverrideGenerator.kt
index d6d8c9b368d..216efafe8d0 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/FakeOverrideGenerator.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/FakeOverrideGenerator.kt
@@ -34,6 +34,7 @@ import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.IdSignature
+import org.jetbrains.kotlin.ir.util.isComposite
 import org.jetbrains.kotlin.ir.util.parentAsClass
 import org.jetbrains.kotlin.load.java.JavaDescriptorVisibilities
 import org.jetbrains.kotlin.name.Name
@@ -231,7 +232,7 @@ class FakeOverrideGenerator(
             // have the same signature.
             // Now we avoid this problem by signature caching,
             // so both FIR overrides correspond to one IR fake override
-            val isTopLevelPrivate = irClass.symbol.signature is IdSignature.CompositeSignature
+            val isTopLevelPrivate = irClass.symbol.signature.isComposite()
             signatureComposer.composeSignature(fakeOverrideFirDeclaration, forceTopLevelPrivate = isTopLevelPrivate)
         }?.takeIf { it.parent == irClass }
             ?: createIrDeclaration(
@@ -283,7 +284,7 @@ class FakeOverrideGenerator(
         }
     }
 
-    fun createFirFunctionFakeOverride(
+    internal fun createFirFunctionFakeOverride(
         klass: FirClass,
         irClass: IrClass,
         originalSymbol: FirNamedFunctionSymbol,
@@ -301,7 +302,7 @@ class FakeOverrideGenerator(
         scope
     )
 
-    fun createFirPropertyFakeOverride(
+    internal fun createFirPropertyFakeOverride(
         klass: FirClass,
         irClass: IrClass,
         originalSymbol: FirPropertySymbol,
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
index 61baf9427cb..99934f96e91 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
@@ -26,10 +26,7 @@ import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.IrSimpleType
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
-import org.jetbrains.kotlin.ir.util.DeserializableClass
-import org.jetbrains.kotlin.ir.util.IdSignature
-import org.jetbrains.kotlin.ir.util.isEnumClass
-import org.jetbrains.kotlin.ir.util.isObject
+import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.OperatorNameConventions
 import org.jetbrains.kotlin.utils.addIfNotNull
@@ -150,7 +147,7 @@ class Fir2IrLazyClass(
     }
 
     override val declarations: MutableList<IrDeclaration> by lazyVar(lock) {
-        val isTopLevelPrivate = symbol.signature is IdSignature.CompositeSignature
+        val isTopLevelPrivate = symbol.signature.isComposite()
         val result = mutableListOf<IrDeclaration>()
         // NB: it's necessary to take all callables from scope,
         // e.g. to avoid accessing un-enhanced Java declarations with FirJavaTypeRef etc. inside
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyProperty.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyProperty.kt
index 78ace9414fa..d7aa1cdf7ad 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyProperty.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyProperty.kt
@@ -32,7 +32,7 @@ import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.ir.expressions.IrExpressionBody
 import org.jetbrains.kotlin.ir.symbols.IrPropertySymbol
-import org.jetbrains.kotlin.ir.util.IdSignature
+import org.jetbrains.kotlin.ir.util.isComposite
 
 class Fir2IrLazyProperty(
     components: Fir2IrComponents,
@@ -165,7 +165,7 @@ class Fir2IrLazyProperty(
             fir,
             isSetter = false,
             containingClass?.symbol?.toLookupTag(),
-            forceTopLevelPrivate = symbol.signature is IdSignature.CompositeSignature
+            forceTopLevelPrivate = symbol.signature.isComposite()
         )!!
         symbolTable.declareSimpleFunction(signature, symbolFactory = { Fir2IrSimpleFunctionSymbol(signature) }) { symbol ->
             Fir2IrLazyPropertyAccessor(
@@ -199,7 +199,7 @@ class Fir2IrLazyProperty(
                 fir,
                 isSetter = true,
                 containingClass?.symbol?.toLookupTag(),
-                forceTopLevelPrivate = symbol.signature is IdSignature.CompositeSignature
+                forceTopLevelPrivate = symbol.signature.isComposite()
             )!!
             symbolTable.declareSimpleFunction(signature, symbolFactory = { Fir2IrSimpleFunctionSymbol(signature) }) { symbol ->
                 Fir2IrLazyPropertyAccessor(
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt
index 17ee395046a..c33c5d0fea8 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt
@@ -1256,3 +1256,6 @@ private fun computeAllOverridden(function: IrSimpleFunction, result: MutableSet<
 
 fun IrBuiltIns.getKFunctionType(returnType: IrType, parameterTypes: List<IrType>) =
     kFunctionN(parameterTypes.size).typeWith(parameterTypes + returnType)
+
+fun IdSignature?.isComposite(): Boolean =
+    this is IdSignature.CompositeSignature