diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
index b6aa79c5e8b..83f3d8bddd2 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/substitution/ConeSubstitutor.kt
@@ -87,7 +87,7 @@ abstract class AbstractConeSubstitutor : ConeSubstitutor() {
     }
 
     private fun ConeDefinitelyNotNullType.substituteOriginal(): ConeDefinitelyNotNullType? {
-        return ConeDefinitelyNotNullType.create(substituteType(original)?.withNullability(ConeNullability.NOT_NULL) ?: original)
+        return ConeDefinitelyNotNullType.create(substituteOrNull(original)?.withNullability(ConeNullability.NOT_NULL) ?: original)
     }
 
     private fun ConeFlexibleType.substituteBounds(): ConeFlexibleType? {
diff --git a/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.kt b/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.kt
index f7540c3e987..4a982f1cc1d 100644
--- a/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.kt
+++ b/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.kt
@@ -32,8 +32,7 @@ public class DiagnosticFactory<D extends EmptyDiagnostic> {
 }
 
 // FILE: DiagnosticFactory0.java
-
-public class DiagnosticFactory0<E extends Element> extends DiagnosticFactory<Diagnostic> {}
+public class DiagnosticFactory0<E extends Element> extends DiagnosticFactory<Diagnostic<E>> {}
 
 // FILE: test.kt
 
@@ -54,5 +53,5 @@ private val DERIVED_FACTORY = DiagnosticFactory0<DerivedElement>()
 fun createViaFactory(d: EmptyDiagnostic) {
     val casted = DERIVED_FACTORY.cast(d)
     val element = casted.element
-    <!INAPPLICABLE_CANDIDATE!>Fix<!>(element)
+    Fix(element)
 }
diff --git a/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.txt b/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.txt
index 2691596ff7e..a46da2826fb 100644
--- a/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.txt
+++ b/compiler/fir/resolve/testData/resolve/expresssions/genericDiagnostic.txt
@@ -16,7 +16,7 @@ FILE: test.kt
     private final val DERIVED_FACTORY: R|DiagnosticFactory0<DerivedElement>| = R|/DiagnosticFactory0.DiagnosticFactory0|<R|DerivedElement|>()
         private get(): R|DiagnosticFactory0<DerivedElement>|
     public final fun createViaFactory(d: R|EmptyDiagnostic|): R|kotlin/Unit| {
-        lval casted: R|Diagnostic<*>!| = R|/DERIVED_FACTORY|.R|FakeOverride</DiagnosticFactory.cast: R|Diagnostic<*>!|>|(R|<local>/d|)
-        lval element: R|Element!| = R|<local>/casted|.R|/Diagnostic.element|
-        <Inapplicable(INAPPLICABLE): [/Fix.Fix]>#(R|<local>/element|)
+        lval casted: R|Diagnostic<DerivedElement>!| = R|/DERIVED_FACTORY|.R|FakeOverride</DiagnosticFactory.cast: R|Diagnostic<DerivedElement>!|>|(R|<local>/d|)
+        lval element: R|DerivedElement!| = R|<local>/casted|.R|/Diagnostic.element|
+        R|/Fix.Fix|(R|<local>/element|)
     }