diff --git a/lib/ngtcp2_conn.h b/lib/ngtcp2_conn.h
index 391461d0aa0930ce64258317f0a12a1ea0dda4b9..388c1c70bba38e877a6bae1204651e0a00f6b96e 100644
--- a/lib/ngtcp2_conn.h
+++ b/lib/ngtcp2_conn.h
@@ -350,7 +350,7 @@ struct ngtcp2_conn {
   struct {
     /* strmq contains ngtcp2_strm which has frames to send. */
     ngtcp2_pq strmq;
-    /* ack is ACK frame.  The underlying buffer is resused. */
+    /* ack is ACK frame.  The underlying buffer is reused. */
     ngtcp2_frame *ack;
     /* max_ack_blks is the number of additional ngtcp2_ack_blk which
        ack can contain. */