diff --git a/pkg/yaml/validation/error.go b/pkg/yaml/validation/error.go
index 1a8450e..b8dc15c 100644
--- a/pkg/yaml/validation/error.go
+++ b/pkg/yaml/validation/error.go
@@ -28,12 +28,15 @@ const (
 	ErrDocumentValidationFailed
 	ErrSchemaNotFound
 	ErrRead
+	ErrUnknown
 )
 
 func (k ErrorKind) Error() string {
 	return k.String()
 }
 
+const unknownErrString = "Unknown"
+
 func (k ErrorKind) String() string {
 	switch k {
 	case ErrKindChangesValidationFailed:
@@ -48,8 +51,10 @@ func (k ErrorKind) String() string {
 		return "SchemaNotFound"
 	case ErrRead:
 		return "ReadError"
+	case ErrUnknown:
+		return unknownErrString
 	default:
-		return "unknown"
+		return unknownErrString
 	}
 }