diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
index 15f92fa2268..c81a6ca15ee 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.name.FqNameUnsafe;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
+import org.jetbrains.kotlin.resolve.descriptorUtil.DescriptorUtilsKt;
 import org.jetbrains.kotlin.resolve.scopes.ChainedMemberScope;
 import org.jetbrains.kotlin.resolve.scopes.MemberScope;
 import org.jetbrains.kotlin.storage.MemoizedFunctionToNotNull;
@@ -64,7 +65,6 @@ public abstract class KotlinBuiltIns {
     private ModuleDescriptorImpl builtInsModule;
 
     private final NotNullLazyValue<Primitives> primitives;
-    private final MemoizedFunctionToNotNull<ModuleDescriptor, UnsignedPrimitives> unsignedPrimitives;
     private final NotNullLazyValue<PackageFragments> packageFragments;
 
     private final MemoizedFunctionToNotNull<Name, ClassDescriptor> builtInClassesByName;
@@ -114,29 +114,6 @@ public abstract class KotlinBuiltIns {
             }
         });
 
-        this.unsignedPrimitives = storageManager.createMemoizedFunction(new Function1<ModuleDescriptor, UnsignedPrimitives>() {
-            @Override
-            public UnsignedPrimitives invoke(ModuleDescriptor module) {
-                Map<KotlinType, SimpleType> unsignedKotlinTypeToKotlinArrayType = new HashMap<KotlinType, SimpleType>();
-                Map<SimpleType, SimpleType> kotlinArrayTypeToUnsignedKotlinType = new HashMap<SimpleType, SimpleType>();
-                for (UnsignedType unsigned : UnsignedType.values()) {
-                    ClassDescriptor descriptor = FindClassInModuleKt.findClassAcrossModuleDependencies(module, unsigned.getClassId());
-                    if (descriptor == null) continue;
-
-                    ClassDescriptor arrayDescriptor =
-                            FindClassInModuleKt.findClassAcrossModuleDependencies(module, unsigned.getArrayClassId());
-                    if (arrayDescriptor == null) continue;
-
-                    SimpleType type = descriptor.getDefaultType();
-                    SimpleType arrayType = arrayDescriptor.getDefaultType();
-
-                    unsignedKotlinTypeToKotlinArrayType.put(type, arrayType);
-                    kotlinArrayTypeToUnsignedKotlinType.put(arrayType, type);
-                }
-                return new UnsignedPrimitives(unsignedKotlinTypeToKotlinArrayType, kotlinArrayTypeToUnsignedKotlinType);
-            }
-        });
-
         this.builtInClassesByName = storageManager.createMemoizedFunction(new Function1<Name, ClassDescriptor>() {
             @Override
             public ClassDescriptor invoke(Name name) {
@@ -824,8 +801,7 @@ public abstract class KotlinBuiltIns {
 
         ModuleDescriptor module = DescriptorUtils.getContainingModuleOrNull(notNullArrayType);
         if (module != null) {
-            //noinspection SuspiciousMethodCalls
-            SimpleType unsignedType = unsignedPrimitives.invoke(module).kotlinArrayTypeToUnsignedKotlinType.get(notNullArrayType);
+            KotlinType unsignedType = getElementTypeForUnsignedArray(notNullArrayType, module);
             if (unsignedType != null) return unsignedType;
         }
 
@@ -833,6 +809,24 @@ public abstract class KotlinBuiltIns {
         throw new IllegalStateException("not array: " + arrayType);
     }
 
+    @Nullable
+    private static KotlinType getElementTypeForUnsignedArray(@NotNull KotlinType notNullArrayType, @NotNull ModuleDescriptor module) {
+        ClassifierDescriptor descriptor = notNullArrayType.getConstructor().getDeclarationDescriptor();
+        if (descriptor == null) return null;
+        if (!UnsignedTypes.INSTANCE.isShortNameOfUnsignedArray(descriptor.getName())) return null;
+
+        ClassId arrayClassId = DescriptorUtilsKt.getClassId(descriptor);
+        if (arrayClassId == null) return null;
+
+        ClassId elementClassId = UnsignedTypes.INSTANCE.getUnsignedClassIdByArrayClassId(arrayClassId);
+        if (elementClassId == null) return null;
+
+        ClassDescriptor elementClassDescriptor = FindClassInModuleKt.findClassAcrossModuleDependencies(module, elementClassId);
+        if (elementClassDescriptor == null) return null;
+
+        return elementClassDescriptor.getDefaultType();
+    }
+
     @NotNull
     public SimpleType getPrimitiveArrayKotlinType(@NotNull PrimitiveType primitiveType) {
         return primitives.invoke().primitiveTypeToArrayKotlinType.get(primitiveType);
@@ -847,10 +841,21 @@ public abstract class KotlinBuiltIns {
         if (primitiveArray != null) return primitiveArray;
 
         if (UnsignedTypes.INSTANCE.isUnsignedType(kotlinType)) {
+            if (TypeUtils.isNullableType(kotlinType)) return null;
+
             ModuleDescriptor module = DescriptorUtils.getContainingModuleOrNull(kotlinType);
             if (module == null) return null;
 
-            return unsignedPrimitives.invoke(module).unsignedKotlinTypeToKotlinArrayType.get(kotlinType);
+            ClassId unsignedClassId = DescriptorUtilsKt.getClassId(kotlinType.getConstructor().getDeclarationDescriptor());
+            assert unsignedClassId != null : "unsignedClassId should not be null for unsigned type " + kotlinType;
+
+            ClassId arrayClassId = UnsignedTypes.INSTANCE.getUnsignedArrayClassIdByUnsignedClassId(unsignedClassId);
+            assert arrayClassId != null : "arrayClassId should not be null for unsigned type " + unsignedClassId;
+
+            ClassDescriptor arrayClassDescriptor = FindClassInModuleKt.findClassAcrossModuleDependencies(module, arrayClassId);
+            if (arrayClassDescriptor == null) return null;
+
+            return arrayClassDescriptor.getDefaultType();
         }
 
         return null;
diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/UnsignedType.kt b/core/descriptors/src/org/jetbrains/kotlin/builtins/UnsignedType.kt
index 8ece3896068..e6e0360ec01 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/UnsignedType.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/UnsignedType.kt
@@ -20,12 +20,27 @@ enum class UnsignedType(val classId: ClassId) {
     ULONG(ClassId.fromString("kotlin/ULong"));
 
     val typeName = classId.shortClassName
-    val arrayTypeName = Name.identifier(typeName.asString() + "Array")
-    val arrayClassId = ClassId(classId.packageFqName, arrayTypeName)
+    val arrayClassId = ClassId(classId.packageFqName, Name.identifier(typeName.asString() + "Array"))
 }
 
 object UnsignedTypes {
-    val unsignedTypeNames = enumValues<UnsignedType>().map { it.typeName }.toSet()
+    private val unsignedTypeNames = enumValues<UnsignedType>().map { it.typeName }.toSet()
+    private val arrayClassIdToUnsignedClassId = hashMapOf<ClassId, ClassId>()
+    private val unsignedClassIdToArrayClassId = hashMapOf<ClassId, ClassId>()
+
+    private val arrayClassesShortNames: Set<Name> = UnsignedType.values().mapTo(mutableSetOf()) { it.arrayClassId.shortClassName }
+
+    init {
+        for (unsignedType in UnsignedType.values()) {
+            arrayClassIdToUnsignedClassId[unsignedType.arrayClassId] = unsignedType.classId
+            unsignedClassIdToArrayClassId[unsignedType.classId] = unsignedType.arrayClassId
+        }
+    }
+
+    fun isShortNameOfUnsignedArray(name: Name) = name in arrayClassesShortNames
+
+    fun getUnsignedClassIdByArrayClassId(arrayClassId: ClassId): ClassId? = arrayClassIdToUnsignedClassId[arrayClassId]
+    fun getUnsignedArrayClassIdByUnsignedClassId(arrayClassId: ClassId): ClassId? = unsignedClassIdToArrayClassId[arrayClassId]
 
     fun isUnsignedType(type: KotlinType): Boolean {
         if (TypeUtils.noExpectedType(type)) return false
@@ -40,4 +55,4 @@ object UnsignedTypes {
                 container.fqName == KotlinBuiltIns.BUILT_INS_PACKAGE_FQ_NAME &&
                 descriptor.name in UnsignedTypes.unsignedTypeNames
     }
-}
\ No newline at end of file
+}
diff --git a/core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt b/core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt
index dbe64eedfe8..3e9af7a91a9 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt
@@ -72,8 +72,8 @@ val ClassifierDescriptorWithTypeParameters.denotedClassDescriptor: ClassDescript
         else -> throw UnsupportedOperationException("Unexpected descriptor kind: $this")
     }
 
-val ClassifierDescriptorWithTypeParameters.classId: ClassId?
-    get() = containingDeclaration.let { owner ->
+val ClassifierDescriptor?.classId: ClassId?
+    get() = this?.containingDeclaration?.let { owner ->
         when (owner) {
             is PackageFragmentDescriptor -> ClassId(owner.fqName, name)
             is ClassifierDescriptorWithTypeParameters -> owner.classId?.createNestedClassId(name)