diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanDriver.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanDriver.kt
index e8fd1bb2f8f..4687e2f001a 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanDriver.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanDriver.kt
@@ -92,7 +92,7 @@ public fun runTopLevelPhases(konanConfig: KonanConfig, environment: KotlinCoreEn
         markBackingFields(context)
         val serializer = KonanSerializationUtil(context)
         context.serializedLinkData = 
-            serializer.serializeModule(context.moduleDescriptor!!)
+            serializer.serializeModule(context.moduleDescriptor)
         DeserializerDriver(context).dumpAllInlineBodies()
     }
     phaser.phase(KonanPhase.BACKEND) {
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DeepVisitor.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DeepVisitor.kt
index 57625d075ea..810427ceeb5 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DeepVisitor.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/DeepVisitor.kt
@@ -33,7 +33,7 @@ open class DeepVisitor<D>(val worker: DeclarationDescriptorVisitor<Boolean, D>)
     open fun visitChildren(descriptor: DeclarationDescriptor?, data: D): Boolean {
         if (descriptor == null) return true
 
-        return descriptor!!.accept(this, data)
+        return descriptor.accept(this, data)
     }
 
     fun applyWorker(descriptor: DeclarationDescriptor, data: D): Boolean {
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/MetadataGenerator.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/MetadataGenerator.kt
index 6794458c44a..cb98665e2eb 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/MetadataGenerator.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/MetadataGenerator.kt
@@ -31,7 +31,6 @@ fun loadMetadata(configuration: CompilerConfiguration, file: File): ModuleDescri
 
     val reader = MetadataReader(file)
 
-    var metadataAsString: String? = null
     var moduleName: String? = null
     val currentAbiVersion = configuration.get(KonanConfigKeys.ABI_VERSION)
 
@@ -57,7 +56,7 @@ fun loadMetadata(configuration: CompilerConfiguration, file: File): ModuleDescri
     val tableOfContentsAsString = reader.string(dataNode)
 
     val moduleDescriptor = 
-        deserializeModule(configuration, {it->loadPackageFragment(reader, it)}, tableOfContentsAsString!!, moduleName!!)
+        deserializeModule(configuration, {it->loadPackageFragment(reader, it)}, tableOfContentsAsString, moduleName)
 
     return moduleDescriptor
 }
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/IrDescriptorDeserializer.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/IrDescriptorDeserializer.kt
index c1951ee9815..36732c13bf5 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/IrDescriptorDeserializer.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/IrDescriptorDeserializer.kt
@@ -414,7 +414,7 @@ internal class IrDescriptorDeserializer(val context: Context,
         // Special case: for invoke we need to re-synthesize 
         // the invoke() descriptor.
         val invoke = functions.singleOrNull {
-            (it as FunctionDescriptor).isFunctionInvoke ?: false
+            (it as FunctionDescriptor).isFunctionInvoke
         }
 
         if (invoke != null) 
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializeIr.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializeIr.kt
index 226edab990a..16f61f66df4 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializeIr.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializeIr.kt
@@ -772,7 +772,7 @@ internal class IrDeserializer(val context: Context,
         val arguments = mutableListOf<IrExpression>()
 
         argumentProtos.forEach {
-            arguments.add(deserializeExpression(it) as IrExpression)
+            arguments.add(deserializeExpression(it))
         }
         return IrStringConcatenationImpl(start, end, type, arguments)
     }
@@ -974,7 +974,7 @@ internal class IrDeserializer(val context: Context,
 
         val body = deserializeStatement(proto.getBody())
         val function = IrFunctionImpl(start, end, origin, 
-            descriptor as FunctionDescriptor, body as IrBody)
+            descriptor, body as IrBody)
 
         proto.defaultArgumentList.forEach {
             val expr = deserializeExpression(it.value)
@@ -1068,7 +1068,7 @@ internal class IrDeserializer(val context: Context,
     }
 
     fun decodeDeclaration(): IrDeclaration {
-        val proto = (rootFunction as DeserializedSimpleFunctionDescriptor).proto
+        val proto = rootFunction.proto
 
         if (!proto.hasExtension(KonanLinkData.inlineIrBody)) {
             throw KonanIrDeserializationException("$rootFunction doesn't have ir serialized.")
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializerVisitor.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializerVisitor.kt
index 892baef6ebc..b2f3c45b2b8 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializerVisitor.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/serialization/SerializerVisitor.kt
@@ -67,7 +67,7 @@ internal class DeserializerDriver(val context: Context) {
     internal fun dumpAllInlineBodies() {
         if (! context.phase!!.verbose) return
         context.log("Now deserializing all inlines for debugging purpose.")
-        context.moduleDescriptor!!.accept(
+        context.moduleDescriptor.accept(
             InlineBodiesPrinterVisitor(InlineBodyPrinter()), Unit)
     }