diff --git a/compiler/testData/diagnostics/tests/extensions/kt1875.fir.fail b/compiler/testData/diagnostics/tests/extensions/kt1875.fir.fail
new file mode 100644
index 00000000000..34912badfd9
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/extensions/kt1875.fir.fail
@@ -0,0 +1,2 @@
+Failures detected in FirBodyResolveTransformerAdapter, file: /kt1875.fir.kt
+Cause: java.lang.RuntimeException: While resolving call R|<local>/t|?.R|kt1875/T.f|?.invoke#(IntegerLiteral(1))
diff --git a/compiler/testData/ir/irText/expressions/kt30020.fir.txt b/compiler/testData/ir/irText/expressions/kt30020.fir.txt
index 2232e8162cf..5457c14e720 100644
--- a/compiler/testData/ir/irText/expressions/kt30020.fir.txt
+++ b/compiler/testData/ir/irText/expressions/kt30020.fir.txt
@@ -48,9 +48,9 @@ FILE fqName:<root> fileName:/kt30020.kt
         element: CONST Int type=kotlin.Int value=4
       CALL 'public final fun plusAssign <T> (element: T of kotlin.collections.plusAssign): kotlin.Unit [inline,operator] declared in kotlin.collections' type=kotlin.Unit origin=null
         <T>: kotlin.Int
-        $receiver: CALL 'public final fun CHECK_NOT_NULL <T0> (arg0: T0 of kotlin.internal.ir.CHECK_NOT_NULL?): T0 of kotlin.internal.ir.CHECK_NOT_NULL declared in kotlin.internal.ir' type=kotlin.collections.MutableList<kotlin.Int> origin=EXCLEXCL
-          <T0>: kotlin.collections.MutableList<kotlin.Int>
-          arg0: CALL 'public abstract fun <get-xs> (): kotlin.collections.MutableList<kotlin.Any> declared in <root>.X' type=kotlin.collections.MutableList<kotlin.Int> origin=null
+        $receiver: CALL 'public final fun CHECK_NOT_NULL <T0> (arg0: T0 of kotlin.internal.ir.CHECK_NOT_NULL?): T0 of kotlin.internal.ir.CHECK_NOT_NULL declared in kotlin.internal.ir' type=kotlin.collections.MutableList<kotlin.Any> origin=EXCLEXCL
+          <T0>: kotlin.collections.MutableList<kotlin.Any>
+          arg0: CALL 'public abstract fun <get-xs> (): kotlin.collections.MutableList<kotlin.Any> declared in <root>.X' type=kotlin.collections.MutableList<kotlin.Any>? origin=null
             $this: GET_VAR 'nx: <root>.X? declared in <root>.test' type=<root>.X? origin=null
         element: CONST Int type=kotlin.Int value=5
       CALL 'public final fun plusAssign <T> (element: T of kotlin.collections.plusAssign): kotlin.Unit [inline,operator] declared in kotlin.collections' type=kotlin.Unit origin=null