diff --git a/tools/killall5.in b/tools/killall5.in
index 7806ec6..a4b6f2c 100644
--- a/tools/killall5.in
+++ b/tools/killall5.in
@@ -49,7 +49,7 @@ pid_wait() {
 	declare counter
 
 	while pids_exist "$@"; do
-		if (( counter = timeout )); then
+		if (( counter == timeout )); then
 			return 1
 		fi