diff --git a/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js b/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js
index 52679666c5..c2c9df1c26 100644
--- a/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js
+++ b/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js
@@ -691,7 +691,7 @@ ve.ui.MWGalleryDialog.prototype.updateMwData = function ( mwData ) {
 	mwData.attrs.heights = heights || undefined;
 	mwData.attrs.perrow = perrow || undefined;
 	mwData.attrs.showfilename = showFilename ? 'yes' : undefined;
-	mwData.attrs.classes = classes || undefined;
+	mwData.attrs.class = classes || undefined;
 	mwData.attrs.style = styles || undefined;
 
 	// Unset mode attribute if it is the same as the default