diff --git a/Include/fileobject.h b/Include/fileobject.h
index 6120e51..1dde17e 100644
--- a/Include/fileobject.h
+++ b/Include/fileobject.h
@@ -39,7 +39,7 @@
 
 /* A routine to check if a file descriptor can be select()-ed. */
 #ifdef HAVE_SELECT
- #define _PyIsSelectable_fd(FD) (((FD) >= 0) && ((FD) < FD_SETSIZE))
+ #define _PyIsSelectable_fd(FD) ((unsigned int)(FD) < (unsigned int)FD_SETSIZE)
 #else
  #define _PyIsSelectable_fd(FD) (1)
 #endif /* HAVE_SELECT */