diff --git a/tools/testing/selftests/net/hsr/hsr_ping.sh b/tools/testing/selftests/net/hsr/hsr_ping.sh
index df9143538708..183f4a0f19dd 100755
--- a/tools/testing/selftests/net/hsr/hsr_ping.sh
+++ b/tools/testing/selftests/net/hsr/hsr_ping.sh
@@ -197,7 +197,7 @@ do
 		break
 	fi
 	sleep 1
-	let WAIT = WAIT - 1
+	let "WAIT = WAIT - 1"
 done
 
 # Just a safety delay in case the above check didn't handle it.