diff --git a/ant/src/org/jetbrains/kotlin/ant/KotlinAntTaskUtil.kt b/ant/src/org/jetbrains/kotlin/ant/KotlinAntTaskUtil.kt
index 498f10e1afa..57108c33a85 100644
--- a/ant/src/org/jetbrains/kotlin/ant/KotlinAntTaskUtil.kt
+++ b/ant/src/org/jetbrains/kotlin/ant/KotlinAntTaskUtil.kt
@@ -21,12 +21,11 @@ import org.jetbrains.kotlin.preloading.ClassPreloadingUtils
 import java.io.File
 import java.lang.ref.SoftReference
 import java.net.JarURLConnection
-import kotlin.properties.Delegates
 
 object KotlinAntTaskUtil {
     private var classLoaderRef = SoftReference<ClassLoader?>(null)
 
-    private val libPath: File by Delegates.lazy {
+    private val libPath: File by lazy {
         // Find path of kotlin-ant.jar in the filesystem and find kotlin-compiler.jar in the same directory
         val resourcePath = "/" + javaClass.getName().replace('.', '/') + ".class"
         val jarConnection = javaClass.getResource(resourcePath).openConnection() as? JarURLConnection
@@ -36,11 +35,11 @@ object KotlinAntTaskUtil {
         antTaskJarPath.getParentFile()
     }
 
-    val compilerJar: File by Delegates.lazy {
+    val compilerJar: File by lazy {
         File(libPath, "kotlin-compiler.jar").assertExists()
     }
 
-    val runtimeJar: File by Delegates.lazy {
+    val runtimeJar: File by lazy {
         File(libPath, "kotlin-runtime.jar").assertExists()
     }
 
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/Callable.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/Callable.kt
index b877c6897b8..5aed03a2c2b 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/Callable.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/Callable.kt
@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.org.objectweb.asm.Type
 import org.jetbrains.org.objectweb.asm.commons.InstructionAdapter
 
-public trait Callable {
+public interface Callable {
     public val owner: Type
 
     public val dispatchReceiverType: Type?
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ClassBuilderInterceptorExtension.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ClassBuilderInterceptorExtension.kt
index 0ff930d3178..5b22f97d31a 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ClassBuilderInterceptorExtension.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ClassBuilderInterceptorExtension.kt
@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.diagnostics.DiagnosticSink
 import org.jetbrains.kotlin.extensions.ProjectExtensionDescriptor
 import org.jetbrains.kotlin.resolve.BindingContext
 
-public trait ClassBuilderInterceptorExtension {
+public interface ClassBuilderInterceptorExtension {
     companion object : ProjectExtensionDescriptor<ClassBuilderInterceptorExtension>(
             "org.jetbrains.kotlin.classBuilderFactoryInterceptorExtension", javaClass<ClassBuilderInterceptorExtension>())
 
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ExpressionCodegenExtension.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ExpressionCodegenExtension.kt
index 946640931fa..ffb254ad6a6 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ExpressionCodegenExtension.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/extensions/ExpressionCodegenExtension.kt
@@ -27,7 +27,7 @@ import org.jetbrains.kotlin.psi.JetClassOrObject
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.resolve.*
 
-public trait ExpressionCodegenExtension {
+public interface ExpressionCodegenExtension {
     companion object : ProjectExtensionDescriptor<ExpressionCodegenExtension>("org.jetbrains.kotlin.expressionCodegenExtension", javaClass<ExpressionCodegenExtension>())
 
     public class Context(
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/SMAP.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/SMAP.kt
index d5bad814797..332050d2a2d 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/SMAP.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/SMAP.kt
@@ -122,7 +122,7 @@ public open class InlineLambdaSourceMapper(parent: SourceMapper, smap: SMAPAndMe
     }
 }
 
-trait SourceMapper {
+interface SourceMapper {
 
     val resultMappings: List<FileMapping>
     val parent: SourceMapper?
diff --git a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/TryBlockClustering.kt b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/TryBlockClustering.kt
index 8ae9ad836fb..c33582dd718 100644
--- a/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/TryBlockClustering.kt
+++ b/compiler/backend/src/org/jetbrains/kotlin/codegen/inline/TryBlockClustering.kt
@@ -30,7 +30,7 @@ public class SplitPair<T: Interval>(val patchedPart: T, val newPart: T)
 
 class SimpleInterval(override val startLabel: LabelNode, override val endLabel: LabelNode ) : Interval
 
-trait Interval {
+interface Interval {
     val startLabel: LabelNode
     val endLabel: LabelNode
 
@@ -39,12 +39,12 @@ trait Interval {
 
 }
 
-trait SplittableInterval<T: Interval> : Interval {
+interface SplittableInterval<T: Interval> : Interval {
     fun split(splitBy: Interval, keepStart: Boolean): SplitPair<T>
 }
 
 
-trait IntervalWithHandler : Interval {
+interface IntervalWithHandler : Interval {
     val handler: LabelNode
     val type: String?
 }