diff --git a/less/modals.less b/less/modals.less
index 776073d572..8adfd3ad2d 100644
--- a/less/modals.less
+++ b/less/modals.less
@@ -65,7 +65,7 @@
   background-color: @modal-backdrop-bg;
   // Fade for backdrop
   &.fade { .opacity(0); }
-  &.in { .opacity(.5); }
+  &.in { .opacity(@modal-backdrop-opacity); }
 }
 
 // Modal header
diff --git a/less/variables.less b/less/variables.less
index e596215d06..0e58b31957 100644
--- a/less/variables.less
+++ b/less/variables.less
@@ -445,6 +445,7 @@
 @modal-content-fallback-border-color:          #999;
 
 @modal-backdrop-bg:           #000;
+@modal-backdrop-opacity:      .5;
 @modal-header-border-color:   #e5e5e5;
 @modal-footer-border-color:   @modal-header-border-color;