diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/AdditionalIrUtils.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/AdditionalIrUtils.kt
index 84c951777db..8b1414ba3ca 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/AdditionalIrUtils.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/AdditionalIrUtils.kt
@@ -37,7 +37,7 @@ val IrDeclarationParent.kotlinFqName: FqName
     get() = when (this) {
         is IrPackageFragment -> this.fqName
         is IrClass -> {
-            if (origin == IrDeclarationOrigin.FILE_CLASS) {
+            if (isFileClass) {
                 parent.kotlinFqName
             } else {
                 parent.kotlinFqName.child(nameForIrSerialization)