diff --git a/compiler/testData/codegen/box/callableReference/function/getArityViaFunctionImpl.kt b/compiler/testData/codegen/box/callableReference/function/getArityViaFunctionImpl.kt
index 214f7bba8d4..2f6bbdb8022 100644
--- a/compiler/testData/codegen/box/callableReference/function/getArityViaFunctionImpl.kt
+++ b/compiler/testData/codegen/box/callableReference/function/getArityViaFunctionImpl.kt
@@ -9,7 +9,7 @@ import kotlin.test.assertEquals
 import kotlin.jvm.internal.FunctionBase
 
 fun test(f: Function<*>, arity: Int) {
-    assertEquals(arity, (f as FunctionBase).getArity())
+    assertEquals(arity, (f as FunctionBase).arity)
 }
 
 fun foo(s: String, i: Int) {}
diff --git a/compiler/testData/codegen/box/coroutines/featureIntersection/callableReference/function/getArityViaFunctionImpl.kt b/compiler/testData/codegen/box/coroutines/featureIntersection/callableReference/function/getArityViaFunctionImpl.kt
index 86dc2af52b8..100d6ab25c9 100644
--- a/compiler/testData/codegen/box/coroutines/featureIntersection/callableReference/function/getArityViaFunctionImpl.kt
+++ b/compiler/testData/codegen/box/coroutines/featureIntersection/callableReference/function/getArityViaFunctionImpl.kt
@@ -18,7 +18,7 @@ suspend fun builder(c: suspend () -> Unit) {
 }
 
 fun test(f: Function<*>, arity: Int) {
-    assertEquals(arity, (f as FunctionBase).getArity())
+    assertEquals(arity, (f as FunctionBase).arity)
 }
 
 suspend fun foo(s: String, i: Int) {}
diff --git a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KFunctionImpl.kt b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KFunctionImpl.kt
index 3becbc6c60e..e4f0dc32847 100644
--- a/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KFunctionImpl.kt
+++ b/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KFunctionImpl.kt
@@ -37,7 +37,7 @@ internal class KFunctionImpl private constructor(
     private val signature: String,
     descriptorInitialValue: FunctionDescriptor?,
     private val boundReceiver: Any? = CallableReference.NO_RECEIVER
-) : KCallableImpl<Any?>(), KFunction<Any?>, FunctionBase, FunctionWithAllInvokes {
+) : KCallableImpl<Any?>(), KFunction<Any?>, FunctionBase<Any?>, FunctionWithAllInvokes {
     constructor(container: KDeclarationContainerImpl, name: String, signature: String, boundReceiver: Any?)
             : this(container, name, signature, null, boundReceiver)
 
@@ -143,7 +143,7 @@ internal class KFunctionImpl private constructor(
     private fun createConstructorCaller(member: Constructor<*>) =
         if (isBound) FunctionCaller.BoundConstructor(member, boundReceiver) else FunctionCaller.Constructor(member)
 
-    override fun getArity() = caller.arity
+    override val arity: Int get() = caller.arity
 
     override val isInline: Boolean
         get() = descriptor.isInline
diff --git a/libraries/stdlib/coroutines/jvm/src/kotlin/coroutines/jvm/internal/ContinuationImpl.kt b/libraries/stdlib/coroutines/jvm/src/kotlin/coroutines/jvm/internal/ContinuationImpl.kt
index 75884242e39..3cff90891d8 100644
--- a/libraries/stdlib/coroutines/jvm/src/kotlin/coroutines/jvm/internal/ContinuationImpl.kt
+++ b/libraries/stdlib/coroutines/jvm/src/kotlin/coroutines/jvm/internal/ContinuationImpl.kt
@@ -132,13 +132,11 @@ internal interface SuspendFunction
 @SinceKotlin("1.3")
 // Restricted suspension lambdas inherit from this class
 internal abstract class RestrictedSuspendLambda(
-    private val arity: Int,
+    public override val arity: Int,
     completion: Continuation<Any?>?
-) : RestrictedContinuationImpl(completion), FunctionBase, SuspendFunction {
+) : RestrictedContinuationImpl(completion), FunctionBase<Any?>, SuspendFunction {
     constructor(arity: Int) : this(arity, null)
 
-    public override fun getArity(): Int = arity
-
     public override fun toString(): String =
         if (completion == null)
             Reflection.renderLambdaToString(this) // this is lambda
@@ -149,16 +147,14 @@ internal abstract class RestrictedSuspendLambda(
 @SinceKotlin("1.3")
 // Suspension lambdas inherit from this class
 internal abstract class SuspendLambda(
-    private val arity: Int,
+    public override val arity: Int,
     completion: Continuation<Any?>?
-) : ContinuationImpl(completion), FunctionBase, SuspendFunction {
+) : ContinuationImpl(completion), FunctionBase<Any?>, SuspendFunction {
     constructor(arity: Int) : this(arity, null)
 
-    public override fun getArity(): Int = arity
-
     public override fun toString(): String =
         if (completion == null)
             Reflection.renderLambdaToString(this) // this is lambda
         else
             super.toString() // this is continuation
-}
\ No newline at end of file
+}
diff --git a/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.java b/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.kt
similarity index 57%
rename from libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.java
rename to libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.kt
index 6bf4621e45b..2bc09ac3eac 100644
--- a/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.java
+++ b/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionBase.kt
@@ -3,10 +3,8 @@
  * that can be found in the license/LICENSE.txt file.
  */
 
-package kotlin.jvm.internal;
+package kotlin.jvm.internal
 
-import kotlin.Function;
-
-public interface FunctionBase extends Function {
-    int getArity();
+interface FunctionBase<out R> : Function<R> {
+    val arity: Int
 }
diff --git a/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Lambda.kt b/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Lambda.kt
index 4aea692f52e..b4caeb8e9bd 100644
--- a/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Lambda.kt
+++ b/libraries/stdlib/jvm/runtime/kotlin/jvm/internal/Lambda.kt
@@ -7,8 +7,6 @@ package kotlin.jvm.internal
 
 import java.io.Serializable
 
-abstract class Lambda(private val arity: Int) : FunctionBase, Serializable {
-    override fun getArity(): Int = arity
-
+abstract class Lambda<out R>(override val arity: Int) : FunctionBase<R>, Serializable {
     override fun toString(): String = Reflection.renderLambdaToString(this)
 }
diff --git a/libraries/stdlib/jvm/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt b/libraries/stdlib/jvm/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt
index 22140358274..06575edddfa 100644
--- a/libraries/stdlib/jvm/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt
+++ b/libraries/stdlib/jvm/src/kotlin/coroutines/experimental/jvm/internal/CoroutineImpl.kt
@@ -18,7 +18,7 @@ abstract class CoroutineImpl(
     arity: Int,
     @JvmField
     protected var completion: Continuation<Any?>?
-) : Lambda(arity), Continuation<Any?> {
+) : Lambda<Any?>(arity), Continuation<Any?> {
 
     // label == -1 when coroutine cannot be started (it is just a factory object) or has already finished execution
     // label == 0 in initial part of the coroutine