diff --git a/compiler/fir/fir-deserialization/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt b/compiler/fir/fir-deserialization/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
index c9050e906fa..2b16b93595c 100644
--- a/compiler/fir/fir-deserialization/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
+++ b/compiler/fir/fir-deserialization/src/org/jetbrains/kotlin/fir/deserialization/FirTypeDeserializer.kt
@@ -149,7 +149,7 @@ class FirTypeDeserializer(
         if (constructor is ConeTypeParameterLookupTag) {
             return ConeTypeParameterTypeImpl(constructor, isNullable = proto.nullable).let {
                 if (Flags.DEFINITELY_NOT_NULL_TYPE.get(proto.flags))
-                    ConeDefinitelyNotNullType.create(it, moduleData.session.typeContext)
+                    ConeDefinitelyNotNullType.create(it, moduleData.session.typeContext) ?: it
                 else
                     it
             }