diff --git a/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/FakeOverrideChecker.kt b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/FakeOverrideChecker.kt
new file mode 100644
index 00000000000..3f8bdb4e86e
--- /dev/null
+++ b/compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/FakeOverrideChecker.kt
@@ -0,0 +1,80 @@
+package org.jetbrains.kotlin.backend.common.override
+
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
+import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.descriptors.Visibilities
+import org.jetbrains.kotlin.descriptors.findClassAcrossModuleDependencies
+import org.jetbrains.kotlin.ir.IrElement
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.util.*
+import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
+import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
+import org.jetbrains.kotlin.ir.visitors.acceptVoid
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
+import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
+import org.jetbrains.kotlin.resolve.scopes.getDescriptorsFiltered
+
+class FakeOverrideChecker(
+    private val irMangler: KotlinMangler.IrMangler,
+    private val descriptorMangler: KotlinMangler.DescriptorMangler
+) {
+
+    private fun checkOverriddenSymbols(fake: IrOverridableMember) {
+        if (fake !is IrSimpleFunction) return // TODO: we need overridden symbols on IrProperty.
+        fake.overriddenSymbols.forEach { symbol ->
+            assert((symbol.owner.parent as IrClass).declarations.contains(symbol.owner)) {
+                "CHECK overridden symbols: ${fake.render()} refers to ${symbol.owner.render()} which is not a member of ${symbol.owner.parent.render()}"
+            }
+        }
+    }
+
+    private fun validateFakeOverrides(clazz: IrClass) {
+        val classId = clazz.classId ?: return
+        val classDescriptor = clazz.module.module.findClassAcrossModuleDependencies(classId) ?: return
+        // All enum entry overrides look like fake overrides in descriptor enum entries
+        if (classDescriptor.kind == ClassKind.ENUM_ENTRY) return
+
+        val descriptorFakeOverrides = classDescriptor.unsubstitutedMemberScope
+            .getDescriptorsFiltered(DescriptorKindFilter.CALLABLES)
+            .filterIsInstance<CallableMemberDescriptor>()
+            .filter { it.kind == CallableMemberDescriptor.Kind.FAKE_OVERRIDE }
+            .filterNot { it.visibility == Visibilities.PRIVATE || it.visibility == Visibilities.INVISIBLE_FAKE }
+
+        val descriptorSignatures = descriptorFakeOverrides
+            .map { with(descriptorMangler) { it.signatureString }}
+            .sorted()
+
+        val irFakeOverrides = clazz.declarations
+            .filterIsInstance<IrOverridableMember>()
+            .filter { it.isFakeOverride }
+
+        irFakeOverrides.forEach {
+            checkOverriddenSymbols(it)
+        }
+
+        val irSignatures = irFakeOverrides
+            .map { with(irMangler) { it.signatureString }}
+            .sorted()
+
+        assert(descriptorSignatures == irSignatures) {
+            "[IR VALIDATION] Fake override mismatch for ${clazz.fqNameWhenAvailable!!}\n" +
+            "\tDescriptor based: $descriptorSignatures\n" +
+            "\tIR based        : $irSignatures"
+        }
+    }
+
+    fun check(module: IrModuleFragment) {
+        module.acceptVoid(object : IrElementVisitorVoid {
+            override fun visitElement(element: IrElement) {
+                element.acceptChildrenVoid(this)
+            }
+            override fun visitClass(declaration: IrClass) {
+                validateFakeOverrides(declaration)
+                super.visitClass(declaration)
+            }
+            override fun visitFunction(declaration: IrFunction) {
+                // Don't go for function local classes
+            }
+        })
+    }
+}
diff --git a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/klib.kt b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/klib.kt
index 6a3cec379fa..7a47731d226 100644
--- a/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/klib.kt
+++ b/compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/klib.kt
@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.backend.common.extensions.IrGenerationExtension
 import org.jetbrains.kotlin.backend.common.extensions.IrPluginContext
 import org.jetbrains.kotlin.backend.common.extensions.IrPluginContextImpl
 import org.jetbrains.kotlin.backend.common.serialization.DeserializationStrategy
+import org.jetbrains.kotlin.backend.common.serialization.FakeOverrideChecker
 import org.jetbrains.kotlin.backend.common.serialization.KlibIrVersion
 import org.jetbrains.kotlin.backend.common.serialization.knownBuiltins
 import org.jetbrains.kotlin.backend.common.serialization.mangle.ManglerChecker
@@ -162,6 +163,8 @@ fun generateKLib(
     val moduleFragment = psi2IrContext.generateModuleFragmentWithPlugins(project, files, irLinker, expectDescriptorToSymbol)
 
     moduleFragment.acceptVoid(ManglerChecker(JsManglerIr, Ir2DescriptorManglerAdapter(JsManglerDesc)))
+    val fakeOverrideChecker = FakeOverrideChecker(JsManglerIr, JsManglerDesc)
+    irLinker.modules.forEach{ fakeOverrideChecker.check(it) }
 
     val moduleName = configuration[CommonConfigurationKeys.MODULE_NAME]!!
 
@@ -230,6 +233,10 @@ fun loadIr(
             // TODO: not sure whether this check should be enabled by default. Add configuration key for it.
             val mangleChecker = ManglerChecker(JsManglerIr, Ir2DescriptorManglerAdapter(JsManglerDesc))
             moduleFragment.acceptVoid(mangleChecker)
+
+            val fakeOverrideChecker = FakeOverrideChecker(JsManglerIr, JsManglerDesc)
+            irLinker.modules.forEach{ fakeOverrideChecker.check(it) }
+
             irBuiltIns.knownBuiltins.forEach { it.acceptVoid(mangleChecker) }
 
             return IrModuleInfo(moduleFragment, deserializedModuleFragments, irBuiltIns, symbolTable, irLinker)