diff --git a/sys/src/libc/9sys/tm2sec.c b/sys/src/libc/9sys/tm2sec.c
index 8b3a9d967..1959e7980 100644
--- a/sys/src/libc/9sys/tm2sec.c
+++ b/sys/src/libc/9sys/tm2sec.c
@@ -7,5 +7,14 @@ tm2sec(Tm *tm)
 	Tm tt;
 
 	tt = *tm;
+	/*
+	 * The zone offset should be calculated,
+	 * but old code may not init tz member.
+	 * nil it out so we don't access junk.
+	 * while we're at it, old code probably
+	 * leaves junk in nsec.
+	 */
+	tt.nsec = 0;
+	tt.tz = nil;
 	return tmnorm(&tt);
 }