diff --git a/include/mysql_com.h b/include/mysql_com.h
index a226c59bc9b..a3790a44c1d 100644
--- a/include/mysql_com.h
+++ b/include/mysql_com.h
@@ -209,8 +209,6 @@ enum enum_server_command
 #define CLIENT_MULTI_RESULTS    (1UL << 17) /* Enable/disable multi-results */
 #define CLIENT_PS_MULTI_RESULTS (1UL << 18) /* Multi-results in PS-protocol */
 
-#define CLIENT_PLUGIN_AUTH  (1UL << 19) /* Client supports plugin authentication */
-
 #define CLIENT_PLUGIN_AUTH  (1UL << 19) /* Client supports plugin authentication */
 #define CLIENT_CONNECT_ATTRS (1UL << 20) /* Client supports connection attributes */
 /* Enable authentication response packet to be larger than 255 bytes. */