Upon saving, ClangFormat replaces tabs with spaces in one-line functions

Steps to reproduce:

• Delete ~/.config/QtProject
• Launch Qt Creator, enable the experimental ClangFormat plugin, and restart
• Open the attached project in Qt Creator — the project contains a .clang-format file specifying that tabs should be used for indentation
• Open main.cpp
• Move the cursor after the open curly brace and press Enter
• Type return 0; (do not press Enter)
• (Note that the return 0; line is indented using a tab — good)
• File > Save
• (Note that now the return 0; line is indented using 4 spaces — bad)

If I run clang-format main.cpp from the command line, it correctly indents using a tab.

This bug seems to happen only for one-line functions. If the function has 2 or more lines, it correctly indents using tabs.