diff --git a/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.fir.txt b/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.fir.txt
index 1f60d04a326..b789824ebc3 100644
--- a/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.fir.txt
+++ b/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.fir.txt
@@ -4,7 +4,7 @@ FILE: objectDerivedFromInnerClass.kt
             super<R|kotlin/Any|>()
         }
 
-        public final inner class Inner : R|kotlin/Any| {
+        public open inner class Inner : R|kotlin/Any| {
             public Outer.constructor(): R|Outer.Inner| {
                 super<R|kotlin/Any|>()
             }
diff --git a/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.kt b/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.kt
index b3985793836..c4675e18159 100644
--- a/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.kt
+++ b/compiler/fir/analysis-tests/testData/resolve/problems/objectDerivedFromInnerClass.kt
@@ -1,4 +1,4 @@
-class Outer { inner class Inner }
+class Outer { open inner class Inner }
 fun test() {
     val x = object : <!UNRESOLVED_REFERENCE!>Outer.Inner<!>() { }
 }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonDeclarationCheckers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonDeclarationCheckers.kt
index 5344e262373..b0bf92fa2cb 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonDeclarationCheckers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonDeclarationCheckers.kt
@@ -90,6 +90,7 @@ object CommonDeclarationCheckers : DeclarationCheckers() {
             FirMemberPropertiesChecker,
             FirImplementationMismatchChecker,
             FirTypeParametersInObjectChecker,
+            FirSupertypesChecker,
         )
 
     override val regularClassCheckers: Set<FirRegularClassChecker>
@@ -101,7 +102,6 @@ object CommonDeclarationCheckers : DeclarationCheckers() {
             FirDelegationSuperCallInEnumConstructorChecker,
             FirDelegationInInterfaceSyntaxChecker,
             FirEnumClassSimpleChecker,
-            FirSupertypesChecker,
             FirLocalEntityNotAllowedChecker,
             FirManyCompanionObjectsChecker,
             FirMethodOfAnyImplementedInInterfaceChecker,
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirSupertypesChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirSupertypesChecker.kt
index 145959ac309..08e6cf9a78b 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirSupertypesChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirSupertypesChecker.kt
@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
+import org.jetbrains.kotlin.KtFakeSourceElementKind
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
@@ -30,6 +31,7 @@ import org.jetbrains.kotlin.name.StandardClassIds
 
 object FirSupertypesChecker : FirClassChecker() {
     override fun check(declaration: FirClass, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (declaration.source?.kind is KtFakeSourceElementKind) return
         val isInterface = declaration.classKind == ClassKind.INTERFACE
         var nullableSupertypeReported = false
         var extensionFunctionSupertypeReported = false
diff --git a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
index dacb92af749..8a7a9371ea4 100644
--- a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
+++ b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
@@ -5,3 +5,4 @@ interface C<T> {}
 interface D<T> {}
 
 interface Test : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>in<!> Int>, B<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>out<!> Int>, C<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>>?<!REDUNDANT_NULLABLE!>?<!NULLABLE_SUPERTYPE!>?<!><!>, D<Int> {}
+val x = object : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>> {}
diff --git a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.kt b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.kt
index 3b342cc6d35..d3c9983b47c 100644
--- a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.kt
+++ b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.kt
@@ -4,4 +4,5 @@ interface B<T> {}
 interface C<T> {}
 interface D<T> {}
 
-interface Test : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>in<!> Int>, B<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>out<!> Int>, C<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>><!NULLABLE_SUPERTYPE!>?<!><!REDUNDANT_NULLABLE!>?<!><!REDUNDANT_NULLABLE!>?<!>, D<Int> {}
\ No newline at end of file
+interface Test : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>in<!> Int>, B<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>out<!> Int>, C<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>><!NULLABLE_SUPERTYPE!>?<!><!REDUNDANT_NULLABLE!>?<!><!REDUNDANT_NULLABLE!>?<!>, D<Int> {}
+val x = object : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>> {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
index 6bd87e60c65..6e923a15f62 100644
--- a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
@@ -1,5 +1,7 @@
 package
 
+public val x: A<*>
+
 public interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -29,3 +31,4 @@ public interface Test : A<in kotlin.Int>, B<out kotlin.Int>, C<*>?, D<kotlin.Int
     public open override /*4*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*4*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
diff --git a/compiler/testData/diagnostics/tests/inference/underscoredTypeInForbiddenPositions.fir.kt b/compiler/testData/diagnostics/tests/inference/underscoredTypeInForbiddenPositions.fir.kt
index e60b3beab8b..0de15eb660d 100644
--- a/compiler/testData/diagnostics/tests/inference/underscoredTypeInForbiddenPositions.fir.kt
+++ b/compiler/testData/diagnostics/tests/inference/underscoredTypeInForbiddenPositions.fir.kt
@@ -46,7 +46,7 @@ fun test() {
     val x9: (Foo<Float>) -> Int = { x: Foo<<!UNDERSCORE_USAGE_WITHOUT_BACKTICKS, UNRESOLVED_REFERENCE!>_<!>> -> 10 }
 
     val x10 = object : <!UNRESOLVED_REFERENCE!>_<!> {}
-    val x11 = object : Foo<<!UNRESOLVED_REFERENCE, UNRESOLVED_REFERENCE!>_<!>> {}
+    val x11 = object : <!FINAL_SUPERTYPE!>Foo<<!UNRESOLVED_REFERENCE, UNRESOLVED_REFERENCE!>_<!>><!> {}
 
     if (x11 is <!UNRESOLVED_REFERENCE!>_<!>) { }
     if (<!USELESS_IS_CHECK!>x11 is Foo<<!UNRESOLVED_REFERENCE!>_<!>><!>) { }