diff --git a/less/_modal.less b/less/_modal.less
index 456c0449c3..fb05445d36 100644
--- a/less/_modal.less
+++ b/less/_modal.less
@@ -68,8 +68,8 @@
   left: 0;
   background-color: @modal-backdrop-bg;
   // Fade for backdrop
-  &.fade { .opacity(0); }
-  &.in { .opacity(@modal-backdrop-opacity); }
+  &.fade { opacity: 0; }
+  &.in { opacity: @modal-backdrop-opacity; }
 }
 
 // Modal header