diff --git a/app/assets/stylesheets/mobile/magnific-popup.scss b/app/assets/stylesheets/mobile/magnific-popup.scss
index 1c6cdb13a9a..c2ff7391bb0 100644
--- a/app/assets/stylesheets/mobile/magnific-popup.scss
+++ b/app/assets/stylesheets/mobile/magnific-popup.scss
@@ -147,7 +147,9 @@ $caption-subtitle-color:          #BDBDBD !default;
   left: 0;
   top: 0;
   padding: 0 $popup-padding-left;
-  @include box-sizing(border-box);
+  -webkit-box-sizing: border-box;
+     -moz-box-sizing: border-box;
+          box-sizing: border-box;
 }
 
 // Vertical centerer helper
@@ -451,7 +453,9 @@ button::-moz-focus-inner {
     height: auto;
     display: block;
     line-height: 0;
-    @include box-sizing(border-box);
+    -webkit-box-sizing: border-box;
+       -moz-box-sizing: border-box;
+            box-sizing: border-box;
     padding: $image-padding-top 0 $image-padding-bottom;
     margin: 0 auto;
   }
@@ -530,7 +534,9 @@ button::-moz-focus-inner {
           top: auto;
           padding: 3px 5px;
           position: fixed;
-          @include box-sizing(border-box);
+          -webkit-box-sizing: border-box;
+             -moz-box-sizing: border-box;
+                  box-sizing: border-box;
         }
         .mfp-img-mobile .mfp-bottom-bar:empty {
           padding: 0;