diff --git a/homa_timer.c b/homa_timer.c
index dc22461e..c241e77a 100644
--- a/homa_timer.c
+++ b/homa_timer.c
@@ -34,7 +34,7 @@ void homa_timer_check_rpc(struct homa_rpc *rpc)
 		} else {
 			/* >= comparison that handles tick wrap-around. */
 			if ((rpc->done_timer_ticks + homa->request_ack_ticks
-					- 1 - homa->timer_ticks) & 1 << 31) {
+					- 1 - homa->timer_ticks) & 1U << 31) {
 				struct homa_need_ack_hdr h;
 
 				homa_rpc_unlock(rpc);