diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNotImplementedOverrideChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNotImplementedOverrideChecker.kt
index e0a7b880008..26a9204bead 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNotImplementedOverrideChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNotImplementedOverrideChecker.kt
@@ -37,7 +37,7 @@ object FirNotImplementedOverrideChecker : FirClassChecker() {
         val sourceKind = source.kind
         if (sourceKind is FirFakeSourceElementKind && sourceKind != FirFakeSourceElementKind.EnumInitializer) return
         val modality = declaration.modality()
-        if (modality == Modality.ABSTRACT || modality == Modality.SEALED) return
+        val canHaveAbstractDeclarations = modality == Modality.ABSTRACT || modality == Modality.SEALED
         if (declaration is FirRegularClass && declaration.isExpect) return
         val classKind = declaration.classKind
         if (classKind == ClassKind.ANNOTATION_CLASS || classKind == ClassKind.ENUM_CLASS) return
@@ -67,7 +67,7 @@ object FirNotImplementedOverrideChecker : FirClassChecker() {
             classScope.processPropertiesByName(name, ::collectSymbol)
         }
 
-        if (notImplementedSymbols.isNotEmpty()) {
+        if (!canHaveAbstractDeclarations && notImplementedSymbols.isNotEmpty()) {
             val notImplemented = notImplementedSymbols.first().unwrapFakeOverrides().fir
             if (notImplemented.isFromInterfaceOrEnum(context)) {
                 reporter.reportOn(source, ABSTRACT_MEMBER_NOT_IMPLEMENTED, declaration, notImplemented, context)
@@ -75,7 +75,7 @@ object FirNotImplementedOverrideChecker : FirClassChecker() {
                 reporter.reportOn(source, ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED, declaration, notImplemented, context)
             }
         }
-        if (invisibleSymbols.isNotEmpty()) {
+        if (!canHaveAbstractDeclarations && invisibleSymbols.isNotEmpty()) {
             val invisible = invisibleSymbols.first().fir
             if (context.session.languageVersionSettings.supportsFeature(LanguageFeature.ProhibitInvisibleAbstractMethodsInSuperclasses)) {
                 reporter.reportOn(source, INVISIBLE_ABSTRACT_MEMBER_FROM_SUPER, declaration, invisible, context)
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/sealedOnMembers.fir.kt b/compiler/testData/diagnostics/tests/declarationChecks/sealedOnMembers.fir.kt
index fd7e97ebe76..c9061508727 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/sealedOnMembers.fir.kt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/sealedOnMembers.fir.kt
@@ -8,7 +8,7 @@ interface B {
     abstract var bar: Unit
 }
 
-interface C : A, B
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface C<!> : A, B
 
 abstract class D(sealed var x: Int) {
     abstract var y: Unit
diff --git a/compiler/testData/diagnostics/tests/delegation/clashes/propertyTypeMismatch.fir.kt b/compiler/testData/diagnostics/tests/delegation/clashes/propertyTypeMismatch.fir.kt
index 023163cdfec..27c3b9c6d03 100644
--- a/compiler/testData/diagnostics/tests/delegation/clashes/propertyTypeMismatch.fir.kt
+++ b/compiler/testData/diagnostics/tests/delegation/clashes/propertyTypeMismatch.fir.kt
@@ -34,7 +34,7 @@ abstract class Test1 : IStr by CStr(), IInt
 
 abstract class Test2 : IStr, IInt by CInt()
 
-abstract class Test3 : IStr by CStr(), IInt by CInt()
+abstract <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Test3<!> : IStr by CStr(), IInt by CInt()
 
 abstract class Test4 : IStr by CStr(), IGeneric<String>
 
@@ -49,9 +49,9 @@ abstract class Test8 : IGeneric<String> by CGeneric<String>(), IInt
 // Can't test right now due to https://youtrack.jetbrains.com/issue/KT-10258
 // abstract class Test9 : IGeneric<String> by CGeneric<String>(), IGeneric<Int>
 
-abstract class Test10 : IInt by CInt(), IStr by CStr(), IAny by CAny()
+abstract <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Test10<!> : IInt by CInt(), IStr by CStr(), IAny by CAny()
 
-abstract class Test11 : IInt, IStr by CStr(), IAny by CAny()
+abstract <!DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE!>class Test11<!> : IInt, IStr by CStr(), IAny by CAny()
 
 abstract class Test12 : IInt, IStr, IAny by CAny()
 
diff --git a/compiler/testData/diagnostics/tests/delegation/clashes/returnTypeMismatch.fir.kt b/compiler/testData/diagnostics/tests/delegation/clashes/returnTypeMismatch.fir.kt
index 1b7454f373f..d5a08e52976 100644
--- a/compiler/testData/diagnostics/tests/delegation/clashes/returnTypeMismatch.fir.kt
+++ b/compiler/testData/diagnostics/tests/delegation/clashes/returnTypeMismatch.fir.kt
@@ -36,7 +36,7 @@ abstract class Test1 : IStr by CStr(), IInt
 
 abstract class Test2 : IStr, IInt by CInt()
 
-abstract class Test3 : IStr by CStr(), IInt by CInt()
+abstract <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Test3<!> : IStr by CStr(), IInt by CInt()
 
 abstract class Test4 : IStr by CStr(), IGeneric<String>
 
@@ -51,9 +51,9 @@ abstract class Test8 : IGeneric<String> by CGeneric<String>(), IInt
 // Can't test due to https://youtrack.jetbrains.com/issue/KT-10258
 // abstract class Test9 : IGeneric<String> by CGeneric<String>(), IGeneric<Int>
 
-abstract class Test10 : IInt by CInt(), IStr by CStr(), IAny by CAny()
+abstract <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Test10<!> : IInt by CInt(), IStr by CStr(), IAny by CAny()
 
-abstract class Test11 : IInt, IStr by CStr(), IAny by CAny()
+abstract <!DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE!>class Test11<!> : IInt, IStr by CStr(), IAny by CAny()
 
 abstract class Test12 : IInt, IStr, IAny by CAny()
 
diff --git a/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.fir.kt b/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.fir.kt
deleted file mode 100644
index 0d7901d14f0..00000000000
--- a/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.fir.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-interface ILeft {
-    fun foo() {}
-}
-
-interface IRight {
-    fun foo()
-}
-
-interface IDerived : ILeft, IRight
-
-<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class CDerived<!> : ILeft, IRight
-
-abstract class ADerived : ILeft, IRight
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.kt b/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.kt
index 8c06a401c97..83d2d249f6e 100644
--- a/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.kt
+++ b/compiler/testData/diagnostics/tests/java8Overrides/defaultVsAbstract.kt
@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface ILeft {
     fun foo() {}
 }
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity.fir.kt
index 675f9586dc7..54b63c6aae6 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity.fir.kt
@@ -10,9 +10,9 @@ interface B{
     }
 }
 
-interface AB: A, B
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface AB<!>: A, B
 
-interface BA: B, A
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface BA<!>: B, A
 
 
 interface C : A, B {
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity2.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity2.fir.kt
index cde952cd170..8b6e555c7da 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity2.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity2.fir.kt
@@ -9,9 +9,9 @@ interface B{
     }
 }
 
-interface AB: A, B
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface AB<!>: A, B
 
-interface BA: B, A
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface BA<!>: B, A
 
 class C : A, B {
     override fun test() {
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity3.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity3.fir.kt
index 923f86ef6ee..b34e87ce3a2 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity3.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmDefault/superCallAmbiguity3.fir.kt
@@ -9,8 +9,8 @@ interface A {
 interface B{
     fun test()
 }
-interface AB : A, B
-interface BA : B, A
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface AB<!> : A, B
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>interface BA<!> : B, A
 
 class C : A, B {
     override fun test() {