PVS-Studio warning V576 for glibc

typedef unsigned int __uid_t;
typedef __uid_t uid_t;

int
user2netname (...., const uid_t uid, ....)
{
  ....
  sprintf (netname, "%s.%d@%s", OPSYS, uid, dfltdom);
  ....
}

This suspicious code was found in glibc project by PVS-Studio static code analyzer.
Warning message is:
V576 Incorrect format. Consider checking the fourth actual argument of the 'sprintf' function. The SIGNED integer type argument is expected. netname.c 51

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