diff --git a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypeUtils.kt b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypeUtils.kt
index 57443160797..2fd3a13897b 100644
--- a/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypeUtils.kt
+++ b/compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypeUtils.kt
@@ -75,7 +75,7 @@ fun ConeKotlinType.lowerBoundIfFlexible(): ConeSimpleKotlinType {
     }
 }
 
-fun ConeKotlinType.originalIfDefinitelyNotNullable(): ConeKotlinType {
+fun ConeSimpleKotlinType.originalIfDefinitelyNotNullable(): ConeSimpleKotlinType {
     return when (this) {
         is ConeDefinitelyNotNullType -> original
         else -> this