diff --git a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeclarationTable.kt b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeclarationTable.kt
index 2d4da384146..ad901cae8c9 100644
--- a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeclarationTable.kt
+++ b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeclarationTable.kt
@@ -38,7 +38,7 @@ abstract class GlobalDeclarationTable(private val mangler: KotlinMangler, privat
     protected open fun loadKnownBuiltins(builtIns: IrBuiltIns, startIndex: Long): Long {
         var index = startIndex
         builtIns.knownBuiltins.forEach {
-            table[it.owner] = UniqId(index++, false)
+            table[it.owner] = UniqId(index++, false).also { id -> clashTracker.commit(it.owner, id) }
         }
         return index
     }
diff --git a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeserializeDescriptorReference.kt b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeserializeDescriptorReference.kt
index 93c2af7c91e..c85267171a1 100644
--- a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeserializeDescriptorReference.kt
+++ b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/DeserializeDescriptorReference.kt
@@ -29,11 +29,7 @@ abstract class DescriptorReferenceDeserializer(
 ) : DescriptorUniqIdAware {
 
     protected open fun resolveSpecialDescriptor(fqn: FqName) = builtIns.builtIns.getBuiltInClassByFqName(fqn)
-
-    protected abstract fun resolveSpecialDescriptor(fqn: FqName): DeclarationDescriptor
-    abstract fun checkIfSpecialDescriptorId(id: Long): Boolean
-    protected abstract fun getDescriptorIdOrNull(descriptor: DeclarationDescriptor): Long?
-    protected open fun checkIfSpecialDescriptorId(id: Long) = with(mangler) { id.isSpecial }
+    open fun checkIfSpecialDescriptorId(id: Long) = with(mangler) { id.isSpecial }
 
     protected open fun getDescriptorIdOrNull(descriptor: DeclarationDescriptor) =
         if (isBuiltInFunction(descriptor)) {
diff --git a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/IrModuleSerializer.kt b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/IrModuleSerializer.kt
index 7b3dd624984..972fd053bf9 100644
--- a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/IrModuleSerializer.kt
+++ b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/IrModuleSerializer.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.backend.common.serialization
 
 import org.jetbrains.kotlin.backend.common.LoggingContext
+import org.jetbrains.kotlin.builtins.FunctionInterfacePackageFragment
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
 import org.jetbrains.kotlin.library.SerializedIrFile
@@ -20,6 +21,6 @@ abstract class IrModuleSerializer<F : IrFileSerializer>(protected val logger: Lo
     }
 
     fun serializedIrModule(module: IrModuleFragment): SerializedIrModule {
-        return SerializedIrModule(module.files.map { serializeIrFile(it) })
+        return SerializedIrModule(module.files.filter { it.packageFragmentDescriptor !is FunctionInterfacePackageFragment }.map { serializeIrFile(it) })
     }
 }
\ No newline at end of file
diff --git a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsDeclarationTable.kt b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsDeclarationTable.kt
index 324d9dd4ae7..b31b2b0001a 100644
--- a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsDeclarationTable.kt
+++ b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsDeclarationTable.kt
@@ -5,8 +5,8 @@
 
 package org.jetbrains.kotlin.ir.backend.js.lower.serialization.ir
 
-import org.jetbrains.kotlin.backend.common.serialization.DeclarationTable
-import org.jetbrains.kotlin.backend.common.serialization.DescriptorTable
+import org.jetbrains.kotlin.backend.common.serialization.*
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.util.render
 
@@ -27,11 +27,7 @@ class JsUniqIdClashTracker: UniqIdClashTracker {
 }
 
 class JsGlobalDeclarationTable(builtIns: IrBuiltIns) : GlobalDeclarationTable(JsMangler, JsUniqIdClashTracker()) {
-    private val FUNCTION_INDEX_START: Long = loadKnownBuiltins(builtIns, PUBLIC_LOCAL_UNIQ_ID_EDGE)
-
-    override fun computeUniqIdByDeclaration(declaration: IrDeclaration): UniqId {
-        return if (isBuiltInFunction(declaration)) {
-            UniqId(FUNCTION_INDEX_START + builtInFunctionId(declaration), false)
-        } else super.computeUniqIdByDeclaration(declaration)
+    init {
+        loadKnownBuiltins(builtIns, PUBLIC_LOCAL_UNIQ_ID_EDGE)
     }
 }
\ No newline at end of file
diff --git a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsIrLinker.kt b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsIrLinker.kt
index b33d1446e3f..c4f9d735324 100644
--- a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsIrLinker.kt
+++ b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsIrLinker.kt
@@ -23,9 +23,6 @@ class JsIrLinker(
 ) : KotlinIrLinker(logger, builtIns, symbolTable, emptyList(), null, PUBLIC_LOCAL_UNIQ_ID_EDGE),
     DescriptorUniqIdAware by JsDescriptorUniqIdAware {
 
-    override fun getPrimitiveTypeOrNull(symbol: IrClassifierSymbol, hasQuestionMark: Boolean) =
-        builtIns.getPrimitiveTypeOrNullByDescriptor(symbol.descriptor, hasQuestionMark)
-
     override val descriptorReferenceDeserializer =
         JsDescriptorReferenceDeserializer(currentModule, mangler, builtIns)