diff --git a/compiler/serialization/src/org/jetbrains/kotlin/serialization/AnnotationSerializer.kt b/compiler/serialization/src/org/jetbrains/kotlin/serialization/AnnotationSerializer.kt
index e872acdb91a..27e586c8cc1 100644
--- a/compiler/serialization/src/org/jetbrains/kotlin/serialization/AnnotationSerializer.kt
+++ b/compiler/serialization/src/org/jetbrains/kotlin/serialization/AnnotationSerializer.kt
@@ -29,7 +29,7 @@ class AnnotationSerializer(private val stringTable: StringTable) {
         val annotationClass = annotation.type.constructor.declarationDescriptor as? ClassDescriptor
                               ?: error("Annotation type is not a class: ${annotation.type}")
         if (ErrorUtils.isError(annotationClass)) {
-            error("Unresolved annotation type: ${annotation.type}")
+            error("Unresolved annotation type: ${annotation.type} at ${annotation.source.containingFile}")
         }
 
         id = stringTable.getFqNameIndex(annotationClass)