Module tabs are 1px to wide

The tabs on the left side are in total 241px wide, while the margin-left for the module-list is 240px. See these lines of file module_filter_tab.css:

#module-filter-tabs ul {
  width: 239px;
  ...
  border: 1px solid #ccc;
  ...
}

html.js #module-filter-modules {
  margin-left: 240px;
  ...
}

and file dynamic_position.css:

html.js #module-filter-submit {
  ...
  width: 239px;
  border: 1px solid #ccc;
  ...
}

Result: module list is shown below the tabs. By setting the width to 238px or removing the right border this problem is solved. The latter looks visually superior to me:

Screenshot is from a firefox browser.