diff --git a/Src/Modules/system.c b/Src/Modules/system.c
index 1ee61c0..2769f75 100644
--- a/Src/Modules/system.c
+++ b/Src/Modules/system.c
@@ -636,7 +636,7 @@ bin_zsystem_flock(char *nam, char **args, UNUSED(Options ops), UNUSED(int func))
     lck.l_start = 0;
     lck.l_len = 0;  /* lock the whole file */
 
-    if (timeout > 0) {
+    if (timeout != 0) {
 	time_t end = time(NULL) + (time_t)timeout;
 	while (fcntl(flock_fd, F_SETLK, &lck) < 0) {
 	    if (errflag)