diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
index 7ab04636a62..37f78e81ece 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/lazy/Fir2IrLazyClass.kt
@@ -132,7 +132,7 @@ class Fir2IrLazyClass(
                     if (declaration.name !in processedNames) {
                         processedNames += declaration.name
                         scope.processFunctionsByName(declaration.name) {
-                            if (it is FirNamedFunctionSymbol) {
+                            if (it is FirNamedFunctionSymbol && it.callableId.classId == fir.symbol.classId) {
                                 if (it.isAbstractMethodOfAny()) {
                                     return@processFunctionsByName
                                 }
@@ -175,6 +175,11 @@ class Fir2IrLazyClass(
         with(fakeOverrideGenerator) {
             result += getFakeOverrides(fir, processedNames)
         }
+        for (declaration in result) {
+            if (declaration.parent != this) {
+                throw AssertionError()
+            }
+        }
         result
     }