diff --git a/buildSrc/src/main/kotlin/Java9Modularity.kt b/buildSrc/src/main/kotlin/Java9Modularity.kt
index 57ebe4d1c0..e8c41fc1d9 100644
--- a/buildSrc/src/main/kotlin/Java9Modularity.kt
+++ b/buildSrc/src/main/kotlin/Java9Modularity.kt
@@ -131,7 +131,7 @@ object Java9Modularity {
                 jvmTarget = "9"
                 // To support LV override when set in aggregate builds
                 languageVersion = compileTask.kotlinOptions.languageVersion
-                freeCompilerArgs += listOf("-Xjdk-release=9",  "-Xsuppress-version-warnings")
+                freeCompilerArgs += listOf("-Xjdk-release=9",  "-Xsuppress-version-warnings", "-Xexpect-actual-classes")
                 options.optIn.addAll(compileTask.kotlinOptions.options.optIn)
             }
             // work-around for https://youtrack.jetbrains.com/issue/KT-60583