Variable is removed from source when added to the watch window by Drag&Drop

I am using:

SharpDevelop Version : 5.0.0.3652-Beta 1-1300bac3
.NET Version : 4.0.30319.18408
OS Version : Microsoft Windows NT 6.1.7601 Service Pack 1
Current culture : German (Germany) (de-DE)
Current UI language : en
Running under WOW6432, processor architecture: x86-64
Working Set Memory : 338576kb
GC Heap Memory : 234082kb

When I highlight a variable in my source code while debugging and add it to the watch window by drag and drop, the variable is removed from the source code.

e.g.

return result;

I double click on "result", it is highlighted. Then I move it with the mouse to the watch window. The variable " result" appears in the watch window, but my source looks afterwards like this:

return ;

With SharpDevelop 4, the variable was just added to the watch window and the code is not changed.