diff --git a/lib/codemirror.css b/lib/codemirror.css
index 1902ba4abd..a27d83f8bf 100644
--- a/lib/codemirror.css
+++ b/lib/codemirror.css
@@ -33,8 +33,6 @@
   min-width: 20px;
   text-align: right;
   color: #999;
-  -moz-box-sizing: content-box;
-  box-sizing: content-box;
 }
 
 .CodeMirror-guttermarker { color: black; }
@@ -154,14 +152,10 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
   height: 100%;
   outline: none; /* Prevent dragging from highlighting the element */
   position: relative;
-  -moz-box-sizing: content-box;
-  box-sizing: content-box;
 }
 .CodeMirror-sizer {
   position: relative;
   border-right: 30px solid transparent;
-  -moz-box-sizing: content-box;
-  box-sizing: content-box;
 }
 
 /* The fake, visible scrollbars. Used to force redraw during scrolling
@@ -196,8 +190,6 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
 .CodeMirror-gutter {
   white-space: normal;
   height: 100%;
-  -moz-box-sizing: content-box;
-  box-sizing: content-box;
   display: inline-block;
   margin-bottom: -30px;
   /* Hack to make IE7 behave */
@@ -265,6 +257,16 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
   outline: none;
 }
 
+/* Force content-box sizing for the elements where we expect it */
+.CodeMirror-scroll,
+.CodeMirror-sizer,
+.CodeMirror-gutter,
+.CodeMirror-gutters,
+.CodeMirror-linenumber {
+  -moz-box-sizing: content-box;
+  box-sizing: content-box;
+}
+
 .CodeMirror-measure {
   position: absolute;
   width: 100%;