diff --git a/resources/mmv/ui/mmv.ui.canvas.js b/resources/mmv/ui/mmv.ui.canvas.js
index 2a31b7a3d..73dd08d36 100644
--- a/resources/mmv/ui/mmv.ui.canvas.js
+++ b/resources/mmv/ui/mmv.ui.canvas.js
@@ -33,6 +33,12 @@
 	function Canvas( $container, $imageWrapper, $mainWrapper ) {
 		mw.mmv.ui.Element.call( this, $container );
 
+		/**
+		 * @property {boolean}
+		 * @private
+		 */
+		this.dialogOpen = false;
+
 		/**
 		 * @property {mw.mmv.ThumbnailWidthCalculator}
 		 * @private