diff --git a/rhodecode/public/css/codemirror.less b/rhodecode/public/css/codemirror.less
--- a/rhodecode/public/css/codemirror.less
+++ b/rhodecode/public/css/codemirror.less
@@ -298,8 +298,9 @@ div.CodeMirror span.CodeMirror-nonmatchi
 .CodeMirror-gutter,
 .CodeMirror-gutters,
 .CodeMirror-linenumber {
-  -moz-box-sizing: content-box;
-  box-sizing: content-box;
+  /* RhodeCode added !important, to fix diffs rule */
+  -moz-box-sizing: content-box !important;
+  box-sizing: content-box !important;
 }
 
 .CodeMirror-measure {
diff --git a/rhodecode/public/js/src/rhodecode/codemirror.js b/rhodecode/public/js/src/rhodecode/codemirror.js
--- a/rhodecode/public/js/src/rhodecode/codemirror.js
+++ b/rhodecode/public/js/src/rhodecode/codemirror.js
@@ -269,14 +269,13 @@ var initMarkupCodeMirror = function(text
   cmLog.debug('Loading codemirror mode', DEFAULT_RENDERER);
 
   // start listening on changes to make auto-expanded editor
-  cm.on("change", function(instance, changeObj) {
+  cm.on("change", function (instance, changeObj) {
     var height = initialHeight;
     var lines = instance.lineCount();
-    if ( lines > 6 && lines < 20) {
+    if (lines > 6 && lines < 20) {
       height = "auto";
-    }
-    else if (lines >= 20){
-      zheight = 20*15;
+    } else if (lines >= 20) {
+      height = 20 * 15;
     }
     instance.setSize(null, height);
 
@@ -501,15 +500,15 @@ var initCommentBoxCodeMirror = function(
     cm.setOption("mode", DEFAULT_RENDERER);
     CodeMirror.autoLoadMode(cm, DEFAULT_RENDERER); // load rst or markdown mode
     cmLog.debug('Loading codemirror mode', DEFAULT_RENDERER);
+
     // start listening on changes to make auto-expanded editor
-    cm.on("change", function(self) {
+    cm.on("change", function (self) {
       var height = initialHeight;
       var lines = self.lineCount();
-      if ( lines > 6 && lines < 20) {
+      if (lines > 6 && lines < 20) {
         height = "auto";
-      }
-      else if (lines >= 20){
-        zheight = 20*15;
+      } else if (lines >= 20) {
+        height = 20 * 15;
       }
       self.setSize(null, height);
     });