diff --git a/ChangeLog.md b/ChangeLog.md
index 4115d18d3fc..bee50a86def 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -399,6 +399,7 @@
 - [`KT-11778`](https://youtrack.jetbrains.com/issue/KT-11778) Exception in Lombok plugin: Rewrite at slice FUNCTION
 - [`KT-11708`](https://youtrack.jetbrains.com/issue/KT-11708) "Go to declaration" doesn't work on a call to function with SAM conversion on a derived type
 - [`KT-12381`](https://youtrack.jetbrains.com/issue/KT-12381) Prefer not-nullable return type when overriding Java method without nullability annotation
+- [`KT-12647`](https://youtrack.jetbrains.com/issue/KT-12647) Performance improvement for test-related line markers
 
 ### Reflection
 
diff --git a/idea/src/org/jetbrains/kotlin/idea/highlighter/KotlinTestRunLineMarkerContributor.kt b/idea/src/org/jetbrains/kotlin/idea/highlighter/KotlinTestRunLineMarkerContributor.kt
index 77ef3d43ae2..86936309504 100644
--- a/idea/src/org/jetbrains/kotlin/idea/highlighter/KotlinTestRunLineMarkerContributor.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/highlighter/KotlinTestRunLineMarkerContributor.kt
@@ -53,6 +53,8 @@ class KotlinTestRunLineMarkerContributor : RunLineMarkerContributor() {
         val declaration = element.getStrictParentOfType<KtNamedDeclaration>() ?: return null
         if (declaration.nameIdentifier != element) return null
 
+        if (declaration !is KtClassOrObject && declaration !is KtNamedFunction) return null
+
         // To prevent IDEA failing on red code
         if (declaration.resolveToDescriptorIfAny() == null) return null