diff --git a/src/timezone/strftime.c b/src/timezone/strftime.c
index ab8f60e9c8..2f32cf8bdb 100644
--- a/src/timezone/strftime.c
+++ b/src/timezone/strftime.c
@@ -459,7 +459,8 @@ _fmt(const char *format, const struct pg_tm * t, char *pt, const char *ptlim,
 						negative = diff < 0;
 						if (diff == 0)
 						{
-							negative = t->tm_zone[0] == '-';
+							if (t->tm_zone != NULL)
+								negative = t->tm_zone[0] == '-';
 						}
 						if (negative)
 						{