diff --git a/missing_d/mktime.c b/missing_d/mktime.c
index d394ef17..16a944d3 100644
--- a/missing_d/mktime.c
+++ b/missing_d/mktime.c
@@ -79,7 +79,7 @@
 
 #ifndef TIME_T_MIN
 #define TIME_T_MIN (0 < (time_t) -1 ? (time_t) 0 \
-		    : ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1))
+		    : (time_t) (intmax_t) ~ ((uintmax_t) ~ (time_t) 0 >> 1))
 #endif
 #ifndef TIME_T_MAX
 #define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN)