diff --git a/internal/services/media_scanner.go b/internal/services/media_scanner.go
index d3564b3..39a9fb3 100644
--- a/internal/services/media_scanner.go
+++ b/internal/services/media_scanner.go
@@ -2847,8 +2847,10 @@ func (s *MediaScanner) updateMediaItem(ctx context.Context, existing database.Me
 	}
 
 	// Keep user-customized fields, and keep the override set itself intact.
+	// MergeOverrides guarantees a non-nil slice: a nil []string would encode
+	// as SQL NULL and violate metadata_overrides' NOT NULL constraint.
 	utils.ApplyMetadataOverrides(&params, existing)
-	params.MetadataOverrides = existing.MetadataOverrides
+	params.MetadataOverrides = utils.MergeOverrides(existing.MetadataOverrides)
 
 	_, err = s.db.UpdateMediaItem(ctx, params)
 	return err
@@ -2869,7 +2871,10 @@ func (s *MediaScanner) RescanMediaItem(ctx context.Context, mediaItemID pgtype.U
 		if err := s.db.ClearMediaItemMetadataOverrides(ctx, mediaItemID); err != nil {
 			return fmt.Errorf("failed to clear metadata overrides: %w", err)
 		}
-		item.MetadataOverrides = nil
+		// Empty - not nil: pgx encodes a nil []string parameter as SQL NULL,
+		// which would violate the column's NOT NULL constraint when
+		// updateMediaItem writes the row back.
+		item.MetadataOverrides = []string{}
 	}
 
 	folders, err := s.db.GetLibraryFolders(ctx, item.LibraryID)