diff --git a/less/mixins/vendor-prefixes.less b/less/mixins/vendor-prefixes.less
index e2008c8b2e..31f8e2f7ab 100644
--- a/less/mixins/vendor-prefixes.less
+++ b/less/mixins/vendor-prefixes.less
@@ -99,9 +99,12 @@
 
 // Placeholder text
 .placeholder(@color: @input-color-placeholder) {
-  &::-moz-placeholder           { color: @color;   // Firefox
-                                  opacity: 1; } // See https://github.com/twbs/bootstrap/pull/11526
-  &:-ms-input-placeholder       { color: @color; } // Internet Explorer 10+
+  // Firefox
+  &::-moz-placeholder {
+    color: @color;
+    opacity: 1; // See https://github.com/twbs/bootstrap/pull/11526
+  }
+  &:-ms-input-placeholder { color: @color; } // Internet Explorer 10+
   &::-webkit-input-placeholder  { color: @color; } // Safari and Chrome
 }