diff --git a/include/types/http_htx.h b/include/types/http_htx.h
index 4c49b25..95b64cc 100644
--- a/include/types/http_htx.h
+++ b/include/types/http_htx.h
@@ -38,6 +38,36 @@
 	uint16_t       lws_after;
 };
 
+
+/* Structure used to build the header list of an HTTP reply */
+struct http_reply_hdr {
+	struct ist  name;  /* the header name */
+	struct list value; /* the log-format string value */
+	struct list list;  /* header chained list */
+};
+
+#define HTTP_REPLY_EMPTY    0x00 /* the reply has no payload */
+#define HTTP_REPLY_ERRMSG   0x01 /* the reply is an error message */
+#define HTTP_REPLY_ERRFILES 0x02 /* the reply references an http-errors section */
+#define HTTP_REPLY_RAW      0x03 /* the reply use a raw payload */
+#define HTTP_REPLY_LOGFMT   0x04 /* the reply use a log-format payload */
+
+/* Uses by HAProxy to generate internal responses */
+struct http_reply {
+	unsigned char type;                   /* HTTP_REPLY_* */
+	int status;                           /* The response status code */
+	char *ctype;                          /* The response content-type, may be NULL */
+	struct list hdrs;                     /* A list of http_reply_hdr */
+	union {
+		struct list   fmt;            /* A log-format string (type = HTTP_REPLY_LOGFMT) */
+		struct buffer obj;            /* A raw string (type = HTTP_REPLY_RAW) */
+		struct buffer *errmsg;        /* The error message to use as response (type = HTTP_REPLY_ERRMSG).
+					       * may be NULL, if so rely on the proxy error messages */
+		char          *http_errors;   /* The http-errors section to use (type = HTTP_REPLY_ERRFILES).
+					       * Should be resolved during post-check */
+	} body;
+};
+
 /* A custom HTTP error message load from a row file and converted in HTX. The
  * node key is the file path.
  */