diff --git a/include/types/proxy.h b/include/types/proxy.h
index ca24dbf..55afed7 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -152,7 +152,7 @@
 #define PR_O2_SRC_ADDR	0x00100000	/* get the source ip and port for logs */
 
 #define PR_O2_FAKE_KA   0x00200000      /* pretend we do keep-alive with server eventhough we close */
-#define PR_O2_USE_HTX   0x00400000      /* use the HTX representation for the HTTP protocol */
+/* unused : 0x00400000 */
 
 #define PR_O2_EXP_NONE  0x00000000      /* http-check : no expect rule */
 #define PR_O2_EXP_STS   0x00800000      /* http-check expect status */