diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/TypeTranslator.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/TypeTranslator.kt
index 3c790483f43..7e5ef1c46f6 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/TypeTranslator.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/TypeTranslator.kt
@@ -164,11 +164,9 @@ abstract class TypeTranslator(
         return translateType(approximate(commonSupertype.replaceArgumentsWithStarProjections()), variance)
     }
 
-    private fun SimpleType.toIrTypeAbbreviation(): IrTypeAbbreviation {
-        val typeAliasDescriptor = constructor.declarationDescriptor.let {
-            it as? TypeAliasDescriptor
-                ?: throw AssertionError("TypeAliasDescriptor expected: $it")
-        }
+    private fun SimpleType.toIrTypeAbbreviation(): IrTypeAbbreviation? {
+        // Abbreviated type's classifier might not be TypeAliasDescriptor in case it's MockClassDescriptor (not found in dependencies).
+        val typeAliasDescriptor = constructor.declarationDescriptor as? TypeAliasDescriptor ?: return null
         return IrTypeAbbreviationImpl(
             symbolTable.referenceTypeAlias(typeAliasDescriptor),
             isMarkedNullable,
diff --git a/compiler/testData/codegen/box/typealias/kt45308.kt b/compiler/testData/codegen/box/typealias/kt45308.kt
index c4ba5d2921c..de507f30575 100644
--- a/compiler/testData/codegen/box/typealias/kt45308.kt
+++ b/compiler/testData/codegen/box/typealias/kt45308.kt
@@ -1,5 +1,7 @@
-// KT-45308 Psi2ir: "AssertionError: TypeAliasDescriptor expected" caused by using typealias from one module as a type in another module without a transitive dependency
-// IGNORE_BACKEND: JVM_IR
+// This test checks that unresolved typealias in an abbreviated type does not crash the compiler or result in a compilation error.
+// Apparently, there's some demand for this behavior, see KT-45308.
+
+// FIR reports RETURN_TYPE_MISMATCH: Return type mismatch: expected kotlin/String, actual a/A
 // IGNORE_BACKEND_FIR: JVM_IR
 
 // MODULE: a