diff --git a/src/js/image.js b/src/js/image.js
index f5687c85..fc389c6e 100644
--- a/src/js/image.js
+++ b/src/js/image.js
@@ -190,7 +190,11 @@ $.magnificPopup.registerModule('image', {
 				var img = document.createElement('img');
 				img.className = 'mfp-img';
 				if(item.el && item.el.find('img').length) {
-					img.alt = item.el.find('img').attr('alt');
+					// Sometimes the img does not have an alt attribute. jQuery 1.6+ will
+					// then return /undefined/, setting img.alt=String("undefined").
+					if(item.el.find('img').attr('alt')) {
+						img.alt = item.el.find('img').attr('alt');
+					}
 				}
 				item.img = $(img).on('load.mfploader', onLoadComplete).on('error.mfploader', onLoadError);
 				img.src = item.src;