diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt
index 0b4012f7007..92536f30fe4 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt
@@ -585,7 +585,7 @@ class Fir2IrConverter(
                 classifierStorage.getOrCreateIrEnumEntry(declaration, parent as IrClass)
             }
             is FirAnonymousInitializer -> {
-                declarationStorage.getOrCreateIrAnonymousInitializer(declaration, parent as IrClass)
+                declarationStorage.createIrAnonymousInitializer(declaration, parent as IrClass)
             }
             is FirTypeAlias -> {
                 classifierStorage.getCachedTypeAlias(declaration)?.let { irTypeAlias ->
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
index 3b0b6874534..3d644cabbc7 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt
@@ -933,13 +933,20 @@ class Fir2IrDeclarationStorage(
 
     // ------------------------------------ anonymous initializers ------------------------------------
 
-    fun getOrCreateIrAnonymousInitializer(
+    fun createIrAnonymousInitializer(
         anonymousInitializer: FirAnonymousInitializer,
         containingIrClass: IrClass,
     ): IrAnonymousInitializer {
-        return initializerCache.computeIfAbsent(anonymousInitializer) {
-            callablesGenerator.createIrAnonymousInitializer(anonymousInitializer, containingIrClass)
+        val irInitializer = callablesGenerator.createIrAnonymousInitializer(anonymousInitializer, containingIrClass)
+        val alreadyContained = initializerCache.put(anonymousInitializer, irInitializer)
+        require(alreadyContained == null) {
+            "IR for anonymous initializer already exits: ${anonymousInitializer.render()}"
         }
+        return irInitializer
+    }
+
+    fun getIrAnonymousInitializer(anonymousInitializer: FirAnonymousInitializer): IrAnonymousInitializer {
+        return initializerCache.getValue(anonymousInitializer)
     }
 
     // ------------------------------------ callables ------------------------------------
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
index 419dedaa9b8..80becf74009 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
@@ -392,7 +392,7 @@ class Fir2IrVisitor(
         anonymousInitializer: FirAnonymousInitializer,
         data: Any?
     ): IrElement = whileAnalysing(session, anonymousInitializer) {
-        val irAnonymousInitializer = declarationStorage.getOrCreateIrAnonymousInitializer(anonymousInitializer, conversionScope.lastClass()!!)
+        val irAnonymousInitializer = declarationStorage.getIrAnonymousInitializer(anonymousInitializer)
         declarationStorage.enterScope(irAnonymousInitializer.symbol)
         irAnonymousInitializer.body = convertToIrBlockBody(anonymousInitializer.body!!)
         declarationStorage.leaveScope(irAnonymousInitializer.symbol)