| Index: Source/devtools/front_end/UISourceCode.js | 
| diff --git a/Source/devtools/front_end/UISourceCode.js b/Source/devtools/front_end/UISourceCode.js | 
| index 0fb88a2927b285af2e2291efb79bdcb84d274e0b..9c48e4792eff4d3524fd16d85d9ed3ae2462f41d 100644 | 
| --- a/Source/devtools/front_end/UISourceCode.js | 
| +++ b/Source/devtools/front_end/UISourceCode.js | 
| @@ -533,7 +533,8 @@ WebInspector.UISourceCode.prototype = { | 
| */ | 
| setWorkingCopy: function(newWorkingCopy) | 
| { | 
| -        this._mimeType = this.canonicalMimeType(); | 
| +        if (!this._mimeType) | 
| +            this._mimeType = this.canonicalMimeType(); | 
| this._workingCopy = newWorkingCopy; | 
| delete this._workingCopyGetter; | 
| this.dispatchEventToListeners(WebInspector.UISourceCode.Events.WorkingCopyChanged); | 
|  |