Variable re-naming not working

[BFergerson]

File with just this in it. Won't let me rename $fu

match $p isa project has name "<githubRepo>";
$fi isa file; (has_defines: $p, is_defines: $fi) isa defines;
$fi has file_location $file_location;
$fu isa function; (has_defines: $fi, is_defines: $fu) isa defines;
$fu has qualified_name $fu_name;
$fu has commit_sha1 $commit_sha1;
get $file_location, $fu, $fu_name, $commit_sha1;