diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/FirLightClassForClassOrObjectSymbol.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/FirLightClassForClassOrObjectSymbol.kt
index eb713466546..2182452e06d 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/FirLightClassForClassOrObjectSymbol.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/FirLightClassForClassOrObjectSymbol.kt
@@ -13,10 +13,10 @@ import com.intellij.psi.search.SearchScope
 import com.intellij.psi.stubs.IStubElementType
 import com.intellij.psi.stubs.StubElement
 import org.jetbrains.annotations.NonNls
-import org.jetbrains.kotlin.asJava.classes.getOutermostClassOrObject
-import org.jetbrains.kotlin.asJava.classes.lazyPub
+import org.jetbrains.kotlin.asJava.classes.*
 import org.jetbrains.kotlin.asJava.elements.FirLightIdentifier
 import org.jetbrains.kotlin.asJava.elements.KtLightField
+import org.jetbrains.kotlin.idea.asJava.classes.checkIsInheritor
 import org.jetbrains.kotlin.idea.asJava.classes.getOrCreateFirLightClass
 import org.jetbrains.kotlin.idea.asJava.elements.FirLightTypeParameterListForSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.*
@@ -131,9 +131,19 @@ internal abstract class FirLightClassForClassOrObjectSymbol(
 
     override fun isValid(): Boolean = kotlinOrigin?.isValid ?: true
 
-    //TODO: Implement inheritance check via symbols
-    override fun isInheritor(baseClass: PsiClass, checkDeep: Boolean): Boolean =
-        InheritanceImplUtil.isInheritor(this, baseClass, checkDeep)
+    override fun isInheritor(baseClass: PsiClass, checkDeep: Boolean): Boolean {
+        if (manager.areElementsEquivalent(baseClass, this)) return false
+        LightClassInheritanceHelper.getService(project).isInheritor(this, baseClass, checkDeep).ifSure { return it }
+
+        val thisClassOrigin = kotlinOrigin
+        val baseClassOrigin = (baseClass as? KtLightClass)?.kotlinOrigin
+
+        return if (baseClassOrigin != null && thisClassOrigin != null) {
+            thisClassOrigin.checkIsInheritor(baseClassOrigin, checkDeep)
+        } else {
+            InheritanceImplUtil.isInheritor(this, baseClass, checkDeep)
+        }
+    }
 
     override fun toString() =
         "${this::class.java.simpleName}:${kotlinOrigin?.getDebugText()}"
diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/KtFirBasedFakeLightClass.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/KtFirBasedFakeLightClass.kt
index a1348a8ece4..9697cb0a4d9 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/KtFirBasedFakeLightClass.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/KtFirBasedFakeLightClass.kt
@@ -9,8 +9,8 @@ import com.intellij.psi.PsiClass
 import org.jetbrains.kotlin.asJava.classes.KtFakeLightClass
 import org.jetbrains.kotlin.asJava.classes.KtLightClass
 import org.jetbrains.kotlin.asJava.classes.LightClassInheritanceHelper
+import org.jetbrains.kotlin.idea.asJava.classes.checkIsInheritor
 import org.jetbrains.kotlin.idea.frontend.api.HackToForceAllowRunningAnalyzeOnEDT
-import org.jetbrains.kotlin.idea.frontend.api.analyze
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.psiUtil.containingClassOrObject
 
@@ -32,21 +32,6 @@ class KtFirBasedFakeLightClass(kotlinOrigin: KtClassOrObject) :
         LightClassInheritanceHelper.getService(project).isInheritor(this, baseClass, checkDeep).ifSure { return it }
 
         val baseClassOrigin = (baseClass as? KtLightClass)?.kotlinOrigin ?: return false
-
-        return analyze(kotlinOrigin) {
-
-            val thisSymbol = kotlinOrigin.getClassOrObjectSymbol()
-            val baseSymbol = baseClassOrigin.getClassOrObjectSymbol()
-
-            if (thisSymbol == baseSymbol) return@analyze false
-
-            val baseType = baseSymbol.buildTypeForSymbol()
-
-            if (checkDeep) {
-                thisSymbol.buildTypeForSymbol().isSubTypeOf(baseType)
-            } else {
-                thisSymbol.superTypes.any { baseType.isEqualTo(it.type) }
-            }
-        }
+        return kotlinOrigin.checkIsInheritor(baseClassOrigin, checkDeep)
     }
 }
\ No newline at end of file
diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/firLightClassUtils.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/firLightClassUtils.kt
index 8fee9ca1004..38ddfbea1ed 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/firLightClassUtils.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/asJava/classes/firLightClassUtils.kt
@@ -10,10 +10,7 @@ import com.intellij.psi.PsiReferenceList
 import com.intellij.psi.util.CachedValueProvider
 import com.intellij.psi.util.CachedValuesManager
 import org.jetbrains.kotlin.analyzer.KotlinModificationTrackerService
-import org.jetbrains.kotlin.asJava.classes.KotlinSuperTypeListBuilder
-import org.jetbrains.kotlin.asJava.classes.KtLightClass
-import org.jetbrains.kotlin.asJava.classes.METHOD_INDEX_BASE
-import org.jetbrains.kotlin.asJava.classes.shouldNotBeVisibleAsLightClass
+import org.jetbrains.kotlin.asJava.classes.*
 import org.jetbrains.kotlin.asJava.elements.KtLightField
 import org.jetbrains.kotlin.asJava.elements.KtLightMethod
 import org.jetbrains.kotlin.descriptors.annotations.AnnotationUseSiteTarget
@@ -330,4 +327,22 @@ internal fun KtSymbolWithMembers.createInnerClasses(manager: PsiManager): List<F
     //    result.add(KtLightClassForInterfaceDefaultImpls(classOrObject))
     //}
     return result
-}
\ No newline at end of file
+}
+
+@OptIn(HackToForceAllowRunningAnalyzeOnEDT::class)
+internal fun KtClassOrObject.checkIsInheritor(baseClassOrigin: KtClassOrObject, checkDeep: Boolean): Boolean {
+    return analyze(this) {
+        val thisSymbol = this@checkIsInheritor.getClassOrObjectSymbol()
+        val baseSymbol = baseClassOrigin.getClassOrObjectSymbol()
+
+        if (thisSymbol == baseSymbol) return@analyze false
+
+        val baseType = baseSymbol.buildTypeForSymbol()
+
+        if (checkDeep) {
+            thisSymbol.buildTypeForSymbol().isSubTypeOf(baseType)
+        } else {
+            thisSymbol.superTypes.any { baseType.isEqualTo(it.type) }
+        }
+    }
+}