diff --git a/include/types/checks.h b/include/types/checks.h
index 867d2f7..8cf1c62 100644
--- a/include/types/checks.h
+++ b/include/types/checks.h
@@ -141,7 +141,7 @@
 	short status, code;			/* check result, check code */
 	unsigned short port;			/* the port to use for the health checks */
 	char desc[HCHK_DESC_LEN];		/* health check description */
-	char use_ssl;				/* use SSL for health checks (1: on, 0: server mode, -1: off) */
+	signed char use_ssl;			/* use SSL for health checks (1: on, 0: server mode, -1: off) */
 	int send_proxy;				/* send a PROXY protocol header with checks */
 	struct tcpcheck_rules *tcpcheck_rules;	/* tcp-check send / expect rules */
 	struct tcpcheck_rule *current_step;     /* current step when using tcpcheck */
diff --git a/include/types/server.h b/include/types/server.h
index a214119..80119a3 100644
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -201,7 +201,7 @@
 	enum obj_type obj_type;                 /* object type == OBJ_TYPE_SERVER */
 	enum srv_state next_state, cur_state;   /* server state among SRV_ST_* */
 	enum srv_admin next_admin, cur_admin;   /* server maintenance status : SRV_ADMF_* */
-	char use_ssl;			        /* ssl enabled (1: on, 0: disabled, -1 forced off)  */
+	signed char use_ssl;		        /* ssl enabled (1: on, 0: disabled, -1 forced off)  */
 	unsigned int pp_opts;                   /* proxy protocol options (SRV_PP_*) */
 	struct server *next;
 	int cklen;				/* the len of the cookie, to speed up checks */