diff --git a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinMultiplatformPlugin.kt b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinMultiplatformPlugin.kt
index 17c4c2570d3..e455cc3fe8f 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinMultiplatformPlugin.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinMultiplatformPlugin.kt
@@ -119,7 +119,7 @@ open class KotlinPlatformImplementationPluginBase(platformName: String) : Kotlin
         }
     }
 
-    protected fun addCommonSourceSetToPlatformSourceSet(commonSourceSet: SourceSet) {
+    protected open fun addCommonSourceSetToPlatformSourceSet(commonSourceSet: SourceSet) {
         val platformTask = platformKotlinTasksBySourceSetName[commonSourceSet.name]
         commonSourceSet.kotlin!!.srcDirs.forEach { platformTask?.source(it) }
     }