diff --git a/mongoose.c b/mongoose.c
index 966178a0..878beba3 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -2639,7 +2639,7 @@ static void send_websocket_handshake_if_requested(struct mg_connection *conn) {
 
 static void ping_idle_websocket_connection(struct connection *conn, time_t t) {
   if (t - conn->ns_conn->last_io_time > MONGOOSE_USE_WEBSOCKET_PING_INTERVAL) {
-    mg_websocket_write(&conn->mg_conn, 0x9, "", 0);
+    mg_websocket_write(&conn->mg_conn, WEBSOCKET_OPCODE_PING, "", 0);
   }
 }
 #else
diff --git a/mongoose.h b/mongoose.h
index f2efd052..ac7ceec2 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -72,6 +72,16 @@ enum mg_event {
 };
 typedef int (*mg_handler_t)(struct mg_connection *, enum mg_event);
 
+// Websocket opcodes, from http://tools.ietf.org/html/rfc6455
+enum {
+  WEBSOCKET_OPCODE_CONTINUATION = 0x0,
+  WEBSOCKET_OPCODE_TEXT = 0x1,
+  WEBSOCKET_OPCODE_BINARY = 0x2,
+  WEBSOCKET_OPCODE_CONNECTION_CLOSE = 0x8,
+  WEBSOCKET_OPCODE_PING = 0x9,
+  WEBSOCKET_OPCODE_PONG = 0xa
+};
+
 // Server management functions
 struct mg_server *mg_create_server(void *server_param, mg_handler_t handler);
 void mg_destroy_server(struct mg_server **);