diff --git a/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/HierarchicalMultiplatformProjectImportingTest.kt b/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/HierarchicalMultiplatformProjectImportingTest.kt
index 4972e47949f..ac51ce8f3ff 100644
--- a/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/HierarchicalMultiplatformProjectImportingTest.kt
+++ b/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/HierarchicalMultiplatformProjectImportingTest.kt
@@ -444,7 +444,7 @@ class HierarchicalMultiplatformProjectImportingTest : MultiplePluginVersionGradl
                 targetPlatform(jvm, js)
             }
             module("my-app") {
-                diagnostics(OrphanSourceSetsImportingDiagnostic::class.java to 1)
+                assertDiagnosticsCount<OrphanSourceSetsImportingDiagnostic>(1)
             }
         }
     }
@@ -536,7 +536,7 @@ class HierarchicalMultiplatformProjectImportingTest : MultiplePluginVersionGradl
         checkProjectStructure(exhaustiveModuleList = false, exhaustiveSourceSourceRootList = false, exhaustiveDependencyList = false) {
 
             module("my-app") {
-                diagnostics(OrphanSourceSetsImportingDiagnostic::class.java to 3)
+                assertDiagnosticsCount<OrphanSourceSetsImportingDiagnostic>(3)
             }
 
             // (jvm, js, native) is highly undesirable
diff --git a/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/projectStructureDSL.kt b/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/projectStructureDSL.kt
index 61d5161a0b8..8da1235e9d7 100644
--- a/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/projectStructureDSL.kt
+++ b/idea/idea-gradle/tests/org/jetbrains/kotlin/gradle/projectStructureDSL.kt
@@ -277,17 +277,14 @@ class ModuleInfo(
     }
 
     @Suppress("UnstableApiUsage")
-    fun diagnostics(vararg expectedByType: Pair<Class<out KotlinImportingDiagnostic>, Int>) {
+    internal inline fun <reified T : KotlinImportingDiagnostic> assertDiagnosticsCount(count: Int) {
         val moduleNode = GradleUtil.findGradleModuleData(module)
         val diagnostics = moduleNode!!.kotlinImportingDiagnosticsContainer!!
-        expectedByType.forEach { (expectedClazz, expectedCount) ->
-            val typedDiagnostics = diagnostics.filterIsInstance(expectedClazz)
-            if (typedDiagnostics.size != expectedCount) {
-                val actualCount = typedDiagnostics.size
-                projectInfo.messageCollector.report(
-                    "Expected number of ${expectedClazz.simpleName} diagnostics $expectedCount doesn't match the actual one: $actualCount"
-                )
-            }
+        val typedDiagnostics = diagnostics.filterIsInstance<T>()
+        if (typedDiagnostics.size != count) {
+            projectInfo.messageCollector.report(
+                "Expected number of ${T::class.java.simpleName} diagnostics $count doesn't match the actual one: ${typedDiagnostics.size}"
+            )
         }
     }
 
diff --git a/idea/kotlin-gradle-tooling/src/KotlinImportingDiagnostic.kt b/idea/kotlin-gradle-tooling/src/KotlinImportingDiagnostic.kt
index 85ff99baaf0..7eff2987dc6 100644
--- a/idea/kotlin-gradle-tooling/src/KotlinImportingDiagnostic.kt
+++ b/idea/kotlin-gradle-tooling/src/KotlinImportingDiagnostic.kt
@@ -8,12 +8,18 @@ package org.jetbrains.kotlin.gradle
 import java.io.Serializable
 
 
-interface KotlinImportingDiagnostic : Serializable
+interface KotlinImportingDiagnostic : Serializable {
+    fun deepCopy(cache: MutableMap<Any, Any>): KotlinImportingDiagnostic
+}
+
+typealias KotlinImportingDiagnosticsContainer = MutableSet<KotlinImportingDiagnostic>
 
 interface KotlinSourceSetImportingDiagnostic : KotlinImportingDiagnostic {
     val kotlinSourceSet: KotlinSourceSet
 }
 
-typealias KotlinImportingDiagnosticsContainer = MutableSet<KotlinImportingDiagnostic>
-
-data class OrphanSourceSetsImportingDiagnostic(override val kotlinSourceSet: KotlinSourceSet) : KotlinSourceSetImportingDiagnostic
\ No newline at end of file
+data class OrphanSourceSetsImportingDiagnostic(override val kotlinSourceSet: KotlinSourceSet) : KotlinSourceSetImportingDiagnostic {
+    override fun deepCopy(cache: MutableMap<Any, Any>): OrphanSourceSetsImportingDiagnostic =
+        (cache[kotlinSourceSet] as? KotlinSourceSet)?.let { OrphanSourceSetsImportingDiagnostic(it) }
+            ?: OrphanSourceSetsImportingDiagnostic(KotlinSourceSetImpl(kotlinSourceSet, cache).apply { cache[kotlinSourceSet] = this })
+}
\ No newline at end of file
diff --git a/idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelImpl.kt b/idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelImpl.kt
index 800341d5d25..1791edf052f 100644
--- a/idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelImpl.kt
+++ b/idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelImpl.kt
@@ -266,7 +266,7 @@ data class KotlinMPPGradleModelImpl(
         ),
         mppModel.kotlinNativeHome,
         mppModel.dependencyMap.map { it.key to it.value.deepCopy(cloningCache) }.toMap(),
-        mppModel.kotlinImportingDiagnostics.toMutableSet()
+        mppModel.kotlinImportingDiagnostics.mapTo(mutableSetOf()) { it.deepCopy(cloningCache) }
     )
 }
 
diff --git a/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingChecker.kt b/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingChecker.kt
index 63417a2a4c2..528ae745103 100644
--- a/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingChecker.kt
+++ b/idea/kotlin-gradle-tooling/src/MultiplatformModelImportingChecker.kt
@@ -14,7 +14,8 @@ internal object OrphanSourceSetImportingChecker : MultiplatformModelImportingChe
         model: KotlinMPPGradleModel,
         reportTo: KotlinImportingDiagnosticsContainer,
         context: MultiplatformModelImportingContext
-    ) = model.sourceSets.values.filter { context.isOrphanSourceSet(it) }
-        .map { OrphanSourceSetsImportingDiagnostic(it) }
-        .forEach { reportTo += it }
+    ) {
+        model.sourceSets.values.filter { context.isOrphanSourceSet(it) }
+            .mapTo(reportTo) { OrphanSourceSetsImportingDiagnostic(it) }
+    }
 }
\ No newline at end of file