diff --git a/src/racket/sconfig.h b/src/racket/sconfig.h
index e101001619..dad9257be6 100644
--- a/src/racket/sconfig.h
+++ b/src/racket/sconfig.h
@@ -768,7 +768,7 @@
 
 #if defined(__x86_64__)
 /* work around a bug in localtime() in 10.6.8 */
-# define MIN_VALID_DATE_SECONDS -67768122973193999
+# define MIN_VALID_DATE_SECONDS -67768040609715600
 #endif
 
 # define FLAGS_ALREADY_SET