diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/builtinSpecialBridges.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/builtinSpecialBridges.kt
index b1e0b8ca40f..3347f640d14 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/builtinSpecialBridges.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/builtinSpecialBridges.kt
@@ -119,7 +119,7 @@ object BuiltinSpecialBridgesUtil {
     ): Boolean {
         if (BuiltinMethodsWithSpecialGenericSignature.getDefaultValueForOverriddenBuiltinFunction(this) == null) return false
 
-        val builtin = getOverriddenBuiltinReflectingJvmDescriptor()!!
+        val builtin = getOverriddenBuiltinReflectingJvmDescriptor() ?: error("Overridden built-in member not found: $this")
         return signatureByDescriptor(this) == signatureByDescriptor(builtin)
     }
 }
diff --git a/compiler/tests/org/jetbrains/kotlin/serialization/builtins/AbstractBuiltInsWithJDKMembersTest.kt b/compiler/tests/org/jetbrains/kotlin/serialization/builtins/AbstractBuiltInsWithJDKMembersTest.kt
index 3b376aa4b47..46919032988 100644
--- a/compiler/tests/org/jetbrains/kotlin/serialization/builtins/AbstractBuiltInsWithJDKMembersTest.kt
+++ b/compiler/tests/org/jetbrains/kotlin/serialization/builtins/AbstractBuiltInsWithJDKMembersTest.kt
@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.serialization.builtins
 
 import com.intellij.psi.search.GlobalSearchScope
+import org.jetbrains.kotlin.builtins.BuiltInsPackageFragment
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns.*
 import org.jetbrains.kotlin.cli.jvm.compiler.CliLightClassGenerationSupport
 import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
@@ -68,7 +69,7 @@ abstract class AbstractBuiltInsWithJDKMembersTest : KotlinTestWithEnvironment()
         val packageFragmentProvider = emptyModule.builtIns.builtInsModule.packageFragmentProvider
 
         for (packageFqName in listOf<FqName>(BUILT_INS_PACKAGE_FQ_NAME, COLLECTIONS_PACKAGE_FQ_NAME, RANGES_PACKAGE_FQ_NAME)) {
-            val loaded = packageFragmentProvider.getPackageFragments(packageFqName).single()
+            val loaded = packageFragmentProvider.getPackageFragments(packageFqName).filterIsInstance<BuiltInsPackageFragment>().single()
             RecursiveDescriptorComparator.validateAndCompareDescriptorWithFile(
                     loaded, configuration,
                     File("compiler/testData/builtin-classes/$builtinVersionName/" + packageFqName.asString().replace('.', '-') + ".txt"))
diff --git a/core/descriptor.loader.java/src/org/jetbrains/kotlin/builtins/JvmBuiltInClassDescriptorFactory.kt b/core/descriptor.loader.java/src/org/jetbrains/kotlin/builtins/JvmBuiltInClassDescriptorFactory.kt
index 7f0f9763bb7..f4671ce44fa 100644
--- a/core/descriptor.loader.java/src/org/jetbrains/kotlin/builtins/JvmBuiltInClassDescriptorFactory.kt
+++ b/core/descriptor.loader.java/src/org/jetbrains/kotlin/builtins/JvmBuiltInClassDescriptorFactory.kt
@@ -31,7 +31,7 @@ class JvmBuiltInClassDescriptorFactory(
 ) : ClassDescriptorFactory {
     private val cloneable by storageManager.createLazyValue {
         ClassDescriptorImpl(
-                moduleDescriptor.getPackage(KOTLIN_FQ_NAME).fragments.single(),
+                moduleDescriptor.getPackage(KOTLIN_FQ_NAME).fragments.filterIsInstance<BuiltInsPackageFragment>().single(),
                 CLONEABLE_NAME, Modality.ABSTRACT, ClassKind.INTERFACE, listOf(moduleDescriptor.builtIns.anyType),
                 SourceElement.NO_SOURCE
         ).apply {
diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/BuiltInFictitiousFunctionClassFactory.kt b/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/BuiltInFictitiousFunctionClassFactory.kt
index f06b0ee882e..b87a78b704a 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/BuiltInFictitiousFunctionClassFactory.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/BuiltInFictitiousFunctionClassFactory.kt
@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.builtins.functions
 
+import org.jetbrains.kotlin.builtins.BuiltInsPackageFragment
 import org.jetbrains.kotlin.builtins.functions.FunctionClassDescriptor.Kind
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
@@ -79,7 +80,7 @@ class BuiltInFictitiousFunctionClassFactory(
         val packageFqName = classId.packageFqName
         val (kind, arity) = parseClassName(className, packageFqName) ?: return null
 
-        val containingPackageFragment = module.getPackage(packageFqName).fragments.single()
+        val containingPackageFragment = module.getPackage(packageFqName).fragments.filterIsInstance<BuiltInsPackageFragment>().single()
 
         return FunctionClassDescriptor(storageManager, containingPackageFragment, kind, arity)
     }
diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/FunctionClassDescriptor.kt b/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/FunctionClassDescriptor.kt
index 1bac28c1695..96dc7cb0a45 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/FunctionClassDescriptor.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/functions/FunctionClassDescriptor.kt
@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.builtins.functions
 
+import org.jetbrains.kotlin.builtins.BuiltInsPackageFragment
 import org.jetbrains.kotlin.builtins.KOTLIN_REFLECT_FQ_NAME
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns.BUILT_INS_PACKAGE_FQ_NAME
 import org.jetbrains.kotlin.descriptors.*
@@ -129,8 +130,8 @@ class FunctionClassDescriptor(
 
             // For KFunction{n}, add corresponding numbered Function{n} class, e.g. Function2 for KFunction2
             if (functionKind == Kind.KFunction) {
-                val module = containingDeclaration.containingDeclaration
-                val kotlinPackageFragment = module.getPackage(BUILT_INS_PACKAGE_FQ_NAME).fragments.single()
+                val packageView = containingDeclaration.containingDeclaration.getPackage(BUILT_INS_PACKAGE_FQ_NAME)
+                val kotlinPackageFragment = packageView.fragments.filterIsInstance<BuiltInsPackageFragment>().single()
 
                 add(kotlinPackageFragment, Kind.Function.numberedClassName(arity))
             }