diff --git a/newlib/ChangeLog b/newlib/ChangeLog
index cc2926b2d..2c7ecc7ea 100644
--- a/newlib/ChangeLog
+++ b/newlib/ChangeLog
@@ -1,3 +1,8 @@
+2011-06-25  Andreas Becker  <becker@se-elektronic.de>
+
+	* libc/time/mktime.c (mktime): Lock global timezone info while
+	accessing it.
+
 2011-06-14  Philip Munts  <phil@munts.net>
 
 	* libc/time/asctime_r.c (asctime_r): Replace call to sprintf with call
diff --git a/newlib/libc/time/mktime.c b/newlib/libc/time/mktime.c
index d75d7cc85..acd5d3aa0 100644
--- a/newlib/libc/time/mktime.c
+++ b/newlib/libc/time/mktime.c
@@ -208,6 +208,8 @@ _DEFUN(mktime, (tim_p),
   tm_isdst = tim_p->tm_isdst > 0  ?  1 : tim_p->tm_isdst;
   isdst = tm_isdst;
 
+  TZ_LOCK;
+
   if (_daylight)
     {
       int y = tim_p->tm_year + YEAR_BASE;
@@ -257,6 +259,8 @@ _DEFUN(mktime, (tim_p),
   else /* otherwise assume std time */
     tim += (time_t) tz->__tzrule[0].offset;
 
+  TZ_UNLOCK;
+
   /* reset isdst flag to what we have calculated */
   tim_p->tm_isdst = isdst;