mjt@ishtar:~$ LIBGL_DEBUG=verbose glxinfo
name of display: :0.0
X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  155 (GLX)
  Minor opcode of failed request:  21 (X_GLXGetFBConfigs)
  Value in failed request:  0x1
  Serial number of failed request:  18
  Current serial number in output stream:  18
mjt@ishtar:~$