diff --git a/core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/DeserializedPackageFragmentImpl.kt b/core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/DeserializedPackageFragmentImpl.kt
index 5863ac88f6c..c8f0c882dcd 100644
--- a/core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/DeserializedPackageFragmentImpl.kt
+++ b/core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/DeserializedPackageFragmentImpl.kt
@@ -30,16 +30,20 @@ abstract class DeserializedPackageFragmentImpl(
     fqName: FqName,
     storageManager: StorageManager,
     module: ModuleDescriptor,
-    protected val proto: ProtoBuf.PackageFragment,
+    proto: ProtoBuf.PackageFragment,
     private val containerSource: DeserializedContainerSource?
 ) : DeserializedPackageFragment(fqName, storageManager, module) {
     protected val nameResolver = NameResolverImpl(proto.strings, proto.qualifiedNames)
 
     override val classDataFinder = ProtoBasedClassDataFinder(proto, nameResolver) { containerSource ?: SourceElement.NO_SOURCE }
 
+    // Temporary storage: until `initialize` is called
+    private var _proto: ProtoBuf.PackageFragment? = proto
     private lateinit var _memberScope: MemberScope
 
     override fun initialize(components: DeserializationComponents) {
+        val proto = _proto ?: error("Repeated call to DeserializedPackageFragmentImpl::initialize")
+        _proto = null
         _memberScope = DeserializedPackageMemberScope(
             this, proto.`package`, nameResolver, containerSource, components,
             classNames = {
diff --git a/js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptPackageFragment.kt b/js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptPackageFragment.kt
index 6d04a34a34f..098078018e4 100644
--- a/js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptPackageFragment.kt
+++ b/js/js.serializer/src/org/jetbrains/kotlin/serialization/js/KotlinJavascriptPackageFragment.kt
@@ -40,11 +40,10 @@ class KotlinJavascriptPackageFragment(
         header: JsProtoBuf.Header,
         configuration: DeserializationConfiguration
 ) : DeserializedPackageFragmentImpl(fqName, storageManager, module, proto, JsContainerSource(fqName, header, configuration)) {
-    val fileMap: Map<Int, FileHolder> by storageManager.createLazyValue {
-        this.proto.getExtension(JsProtoBuf.packageFragmentFiles).fileList.withIndex().associate { (index, file) ->
+    val fileMap: Map<Int, FileHolder> =
+        proto.getExtension(JsProtoBuf.packageFragmentFiles).fileList.withIndex().associate { (index, file) ->
             (if (file.hasId()) file.id else index) to FileHolder(file.annotationList)
         }
-    }
 
     private lateinit var annotationDeserializer: AnnotationDeserializer