diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt
index a94c609dadb..cbd6f335af2 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt
@@ -37,7 +37,7 @@ class FirClassSubstitutionScope(
     }
 
     private fun ConeKotlinType.substitute(): ConeKotlinType? {
-        if (this is ConeTypeParameterType) return substitution[this]
+        if (this is ConeTypeParameterType) return substitution[lookupTag]
 
         val newArguments by lazy { arrayOfNulls<ConeKotlinTypeProjection>(typeArguments.size) }
         var initialized = false
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassUseSiteScope.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassUseSiteScope.kt
index 9676e66a35c..ed295305a6e 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassUseSiteScope.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassUseSiteScope.kt
@@ -72,7 +72,7 @@ class FirClassUseSiteScope(
         val self = (this as AbstractFirBasedSymbol<*>).fir as FirCallableMember
         val overriding = seen.firstOrNull {
             val member = (it as AbstractFirBasedSymbol<*>).fir as FirCallableMember
-            member.isOverride && self.modality != Modality.FINAL
+            self.modality != Modality.FINAL
                     && sameReceivers(member.receiverTypeRef, self.receiverTypeRef)
                     && similarFunctionsOrBothProperties(member, self)
         } // TODO: two or more overrides for one fun?
diff --git a/compiler/fir/resolve/testData/resolve/overrides/simple.kt b/compiler/fir/resolve/testData/resolve/overrides/simple.kt
index 63db053a3be..74f6740c812 100644
--- a/compiler/fir/resolve/testData/resolve/overrides/simple.kt
+++ b/compiler/fir/resolve/testData/resolve/overrides/simple.kt
@@ -8,7 +8,7 @@ open class A {
 
 class B : A() {
     override fun foo(): B = this
-    fun bar(): B = this // Ambiguity, no override here
+    fun bar(): B = this // Ambiguity, no override here (really it's just "missing override" and no ambiguity)
     override fun buz(p: B): B = this //No override as B <!:> A
 
     fun test() {
diff --git a/compiler/fir/resolve/testData/resolve/overrides/simple.txt b/compiler/fir/resolve/testData/resolve/overrides/simple.txt
index 6037f3522cb..b6f7da53fea 100644
--- a/compiler/fir/resolve/testData/resolve/overrides/simple.txt
+++ b/compiler/fir/resolve/testData/resolve/overrides/simple.txt
@@ -32,7 +32,7 @@ FILE: simple.kt
 
         public final function test(): R|kotlin/Unit| {
             R|/B.foo|()
-            <Ambiguity: bar, [/B.bar, /A.bar]>#()
+            R|/B.bar|()
             <Ambiguity: buz, [/B.buz, /A.buz]>#()
         }
 
diff --git a/compiler/fir/resolve/testData/resolve/overrides/simpleFakeOverride.txt b/compiler/fir/resolve/testData/resolve/overrides/simpleFakeOverride.txt
index 725e3ef3029..3c0605669f5 100644
--- a/compiler/fir/resolve/testData/resolve/overrides/simpleFakeOverride.txt
+++ b/compiler/fir/resolve/testData/resolve/overrides/simpleFakeOverride.txt
@@ -15,7 +15,7 @@ FILE: simpleFakeOverride.kt
         public constructor(): super<R|A<Some>|>()
 
         public final function test(): R|kotlin/Unit| {
-            R|FakeOverride</A.foo: R|T|>|(<Unresolved name: Some>#())
+            R|FakeOverride</A.foo: R|Some|>|(<Unresolved name: Some>#())
         }
 
     }
diff --git a/idea/testData/fir/multiModule/mppFakeOverrides/common/common.kt b/idea/testData/fir/multiModule/mppFakeOverrides/common/common.kt
index 1f896a60583..3f3afd1fbee 100644
--- a/idea/testData/fir/multiModule/mppFakeOverrides/common/common.kt
+++ b/idea/testData/fir/multiModule/mppFakeOverrides/common/common.kt
@@ -3,8 +3,9 @@ expect open class A<T>() {
 }
 open class B : A<String>() {
     // Fake: override fun foo(arg: String) = super.foo(arg)
-    // Fake (JVM only) (?): override fun bar(arg: String): String = super.bar(arg)
+    // Fake (JVM only): override fun bar(arg: String): String = super.bar(arg)
 }
 open class C : B() {
-    open fun bar(arg: CharSequence): String = arg.toString()
+    open fun bar(arg: String): String = arg
+    open fun baz(arg: CharSequence): String = arg.toString()
 }
\ No newline at end of file
diff --git a/idea/testData/fir/multiModule/mppFakeOverrides/common/common.txt b/idea/testData/fir/multiModule/mppFakeOverrides/common/common.txt
index 1f6466c07e4..5389d453191 100644
--- a/idea/testData/fir/multiModule/mppFakeOverrides/common/common.txt
+++ b/idea/testData/fir/multiModule/mppFakeOverrides/common/common.txt
@@ -12,8 +12,12 @@ FILE: common.kt
     public open class C : R|B| {
         public constructor(): super<R|B|>()
 
-        public open function bar(arg: R|kotlin/CharSequence|): R|kotlin/String| {
-            return@@@bar <Unresolved name: arg>#.<Unresolved name: toString>#()
+        public open function bar(arg: R|kotlin/String|): R|kotlin/String| {
+            return@@@bar <Unresolved name: arg>#
+        }
+
+        public open function baz(arg: R|kotlin/CharSequence|): R|kotlin/String| {
+            return@@@baz <Unresolved name: arg>#.<Unresolved name: toString>#()
         }
 
     }
diff --git a/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.kt b/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.kt
index 68cfec4a931..54da557b799 100644
--- a/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.kt
+++ b/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.kt
@@ -1,11 +1,12 @@
 actual open class A<T> {
     actual open fun foo(arg: T) {}
     open fun bar(arg: T): T = arg
+    open fun baz(arg: T): T = arg
 }
 class D : C() {
-    // Fake: override fun bar(arg: CharSequence): String = super.bar(arg)
     fun test() {
         foo("")
-        bar("")
+        bar("") // should be resolved to just C.bar
+        baz("") // ambiguity (we have C.bar with CharSequence argument and fake override of A.bar with String argument)
     }
 }
\ No newline at end of file
diff --git a/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.txt b/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.txt
index e2fa8e18717..c257c9e5905 100644
--- a/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.txt
+++ b/idea/testData/fir/multiModule/mppFakeOverrides/jvm/jvm.txt
@@ -9,13 +9,18 @@ FILE: jvm.kt
             return@@@bar <Unresolved name: arg>#
         }
 
+        public open function baz(arg: R|T|): R|T| {
+            return@@@baz <Unresolved name: arg>#
+        }
+
     }
     public final class D : R|C| {
         public constructor(): super<R|C|>()
 
         public final function test(): R|kotlin/Unit| {
             R|FakeOverride</A.foo: R|kotlin/Unit|>|(String())
-            <Ambiguity: bar, [/C.bar, /A.bar]>#(String())
+            R|/C.bar|(String())
+            <Ambiguity: baz, [/C.baz, /A.baz]>#(String())
         }
 
     }
diff --git a/idea/testData/fir/multiModule/overrideWithJava/jvm/B.kt b/idea/testData/fir/multiModule/overrideWithJava/jvm/B.kt
index 897fbd4c8c6..1e8254e92c0 100644
--- a/idea/testData/fir/multiModule/overrideWithJava/jvm/B.kt
+++ b/idea/testData/fir/multiModule/overrideWithJava/jvm/B.kt
@@ -1,6 +1,6 @@
 class B : A() {
     override fun foo(): B = this
-    fun bar(): B = this // Ambiguity, no override here
+    fun bar(): B = this // Here we should have "missing override" but no ambiguity
 
     fun test() {
         foo()
diff --git a/idea/testData/fir/multiModule/overrideWithJava/jvm/B.txt b/idea/testData/fir/multiModule/overrideWithJava/jvm/B.txt
index cdad2d7fc14..ec5ad410d76 100644
--- a/idea/testData/fir/multiModule/overrideWithJava/jvm/B.txt
+++ b/idea/testData/fir/multiModule/overrideWithJava/jvm/B.txt
@@ -12,7 +12,7 @@ FILE: B.kt
 
         public final function test(): R|kotlin/Unit| {
             R|/B.foo|()
-            <Ambiguity: bar, [/B.bar, /A.bar]>#()
+            R|/B.bar|()
         }
 
     }