diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
index 57d7f2e567d..b68131dce4d 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
@@ -20,16 +20,19 @@ import org.jetbrains.kotlin.fir.isSubstitutionOverride
 import org.jetbrains.kotlin.fir.scopes.processAllFunctions
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirValueParameterSymbol
+import org.jetbrains.kotlin.fir.unwrapSubstitutionOverrides
 import org.jetbrains.kotlin.name.Name
 
 object FirMultipleDefaultsInheritedFromSupertypesChecker : FirRegularClassChecker() {
     override fun check(declaration: FirRegularClass, context: CheckerContext, reporter: DiagnosticReporter) {
         declaration.unsubstitutedScope(context).processAllFunctions {
-            if (it.containingClassLookupTag() != declaration.symbol.toLookupTag()) {
+            val originalIfSubstitutionOverride = it.unwrapSubstitutionOverrides()
+
+            if (originalIfSubstitutionOverride.containingClassLookupTag() != declaration.symbol.toLookupTag()) {
                 return@processAllFunctions
             }
 
-            checkFunction(declaration, it, context, reporter)
+            checkFunction(declaration, originalIfSubstitutionOverride, context, reporter)
         }
     }
 
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.fir.kt b/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.fir.kt
deleted file mode 100644
index 69171a53300..00000000000
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.fir.kt
+++ /dev/null
@@ -1,15 +0,0 @@
-interface A<T> {
-    fun foo(x: Int = 42): Int
-}
-
-open class B<K> {
-    fun foo(x: Int = 239) = x
-}
-
-interface C<E> {
-    fun foo(x: Int): Int
-}
-
-open <!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE!>class Z<!><R> : A<R>, B<R>(), C<R>
-
-<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE_DEPRECATION_WARNING!>class N<!><W> : Z<W>()
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.kt b/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.kt
index 4dd2340c5ce..0fe6cdf4fbb 100644
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.kt
+++ b/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndSubstitutionOverrides.kt
@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface A<T> {
     fun foo(x: Int = 42): Int
 }