diff --git a/missing.h b/missing.h
index 16ae97a..6d5d550 100644
--- a/missing.h
+++ b/missing.h
@@ -45,7 +45,7 @@
 #endif
 
 #define CLOCKFD 3
-#define FD_TO_CLOCKID(fd)	((~(clockid_t) (fd) << 3) | CLOCKFD)
+#define FD_TO_CLOCKID(fd)	((clockid_t) ((((unsigned int) ~fd) << 3) | CLOCKFD))
 #define CLOCKID_TO_FD(clk)	((unsigned int) ~((clk) >> 3))
 
 #ifndef HAVE_ONESTEP_SYNC