diff --git a/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingContext.kt b/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingContext.kt
index a8b6bc9d204..85ad316f5ca 100644
--- a/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingContext.kt
+++ b/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingContext.kt
@@ -113,7 +113,7 @@ internal class MultiplatformModelImportingContextImpl(override val project: Proj
     }
 
     // overload for small optimization
-    override fun isOrphanSourceSet(sourceSet: KotlinSourceSet): Boolean = sourceSet in sourceSetToParticipatedCompilations.keys
+    override fun isOrphanSourceSet(sourceSet: KotlinSourceSet): Boolean = sourceSet !in sourceSetToParticipatedCompilations.keys
 
     override fun compilationsBySourceSet(sourceSet: KotlinSourceSet): Collection<KotlinCompilation>? =
         sourceSetToParticipatedCompilations[sourceSet]