diff --git a/sys/include/ape/time.h b/sys/include/ape/time.h
index f5ed975a9..8f567c93e 100644
--- a/sys/include/ape/time.h
+++ b/sys/include/ape/time.h
@@ -67,6 +67,7 @@ extern int nanosleep(const struct timespec *req, struct timespec *rem);
 #ifdef _POSIX_SOURCE
 extern char *tzname[2];
 extern long timezone;
+extern long altzone;
 extern int daylight;
 #endif
 
diff --git a/sys/src/ape/lib/ap/posix/tzset.c b/sys/src/ape/lib/ap/posix/tzset.c
index bcbe59dc7..f4cbac075 100644
--- a/sys/src/ape/lib/ap/posix/tzset.c
+++ b/sys/src/ape/lib/ap/posix/tzset.c
@@ -12,6 +12,7 @@ char *tzname[2] = {
 	std, dst
 };
 long timezone;
+long altzone;
 int daylight;
 
 void
@@ -38,6 +39,7 @@ tzset(void)
 	*p = 0;
 	strncpy(dst, q, sizeof dst);
 	q = p + 1;
+	altzone = - atoi(q);
 	daylight = 1;
 	free(env);
 	return;
@@ -46,6 +48,7 @@ error:
 	strcpy(std, "GMT0");
 	dst[0] = '\0';
 	timezone = 0;
+	altzone = 0;
 	daylight = 0;
 	if(env != 0)
 		free(env);
@@ -54,6 +57,7 @@ error:
 nodst:
 	dst[0] = '\0';
 	daylight = 0;
+	altzone = timezone;
 	free(env);
 	return;
 }