diff --git a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/InternalKotlinSourceSet.kt b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/InternalKotlinSourceSet.kt
index 7df6d87d02b..d6d4823abad 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/InternalKotlinSourceSet.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/InternalKotlinSourceSet.kt
@@ -10,20 +10,19 @@ import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.utils.MutableObservableSet
 import org.jetbrains.kotlin.gradle.utils.ObservableSet
-import org.jetbrains.kotlin.tooling.core.MutableExtras
+import org.jetbrains.kotlin.tooling.core.HasMutableExtras
 
 internal val KotlinSourceSet.internal: InternalKotlinSourceSet
     get() = (this as? InternalKotlinSourceSet) ?: throw IllegalArgumentException(
         "KotlinSourceSet $name (${this::class}) does not implement ${InternalKotlinSourceSet::class.simpleName}"
     )
 
-internal interface InternalKotlinSourceSet : KotlinSourceSet {
+internal interface InternalKotlinSourceSet : KotlinSourceSet, HasMutableExtras {
     val project: Project
     override val dependsOn: ObservableSet<KotlinSourceSet>
     val dependsOnClosure: ObservableSet<KotlinSourceSet>
     val withDependsOnClosure: ObservableSet<KotlinSourceSet>
     val compilations: MutableObservableSet<KotlinCompilation<*>>
-    val extras: MutableExtras
 }
 
 internal val KotlinSourceSet.project: Project get() = this.internal.project