diff --git a/include/proto/sample.h b/include/proto/sample.h
index f0be3fd20..b4d52c5ea 100644
--- a/include/proto/sample.h
+++ b/include/proto/sample.h
@@ -28,7 +28,7 @@
 
 extern const char *smp_to_type[SMP_TYPES];
 
-struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, int line, char **err, struct arg_list *al);
+struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, int line, char **err, struct arg_list *al, char **endptr);
 struct sample_conv *find_sample_conv(const char *kw, int len);
 struct sample *sample_process(struct proxy *px, struct session *sess,
                               struct stream *strm, unsigned int opt,
diff --git a/src/acl.c b/src/acl.c
index 4b8a6d49a..1e32271be 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -321,7 +321,7 @@ struct acl_expr *parse_acl_expr(const char **args, char **err, struct arg_list *
 		 * so, we retrieve a completely parsed expression with args and
 		 * convs already done.
 		 */
-		smp = sample_parse_expr((char **)args, &idx, file, line, err, al);
+		smp = sample_parse_expr((char **)args, &idx, file, line, err, al, NULL);
 		if (!smp) {
 			memprintf(err, "%s in ACL expression '%s'", *err, *args);
 			goto out_return;
diff --git a/src/cfgparse-listen.c b/src/cfgparse-listen.c
index 6d9c1f52e..3c2978c8a 100644
--- a/src/cfgparse-listen.c
+++ b/src/cfgparse-listen.c
@@ -1727,7 +1727,7 @@ int cfg_parse_listen(const char *file, int linenum, char **args, int kwm)
 		}
 
 		curproxy->conf.args.ctx = ARGC_STK;
-		expr = sample_parse_expr(args, &myidx, file, linenum, &errmsg, &curproxy->conf.args);
+		expr = sample_parse_expr(args, &myidx, file, linenum, &errmsg, &curproxy->conf.args, NULL);
 		if (!expr) {
 			ha_alert("parsing [%s:%d] : '%s': %s\n", file, linenum, args[0], errmsg);
 			err_code |= ERR_ALERT | ERR_FATAL;
diff --git a/src/dns.c b/src/dns.c
index f82301857..86147a417 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -2572,7 +2572,7 @@ enum act_parse_ret dns_parse_do_resolve(const char **args, int *orig_arg, struct
 
 	cur_arg = cur_arg + 1;
 
-	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args);
+	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args, NULL);
 	if (!expr)
 		goto do_resolve_parse_error;
 
diff --git a/src/flt_spoe.c b/src/flt_spoe.c
index 4e448dd11..a78e6159e 100644
--- a/src/flt_spoe.c
+++ b/src/flt_spoe.c
@@ -3968,7 +3968,7 @@ cfg_parse_spoe_message(const char *file, int linenum, char **args, int kwm)
 			}
 			arg->expr = sample_parse_expr((char*[]){delim, NULL},
 						      &idx, file, linenum, &errmsg,
-						      &curproxy->conf.args);
+						      &curproxy->conf.args, NULL);
 			if (arg->expr == NULL) {
 				ha_alert("parsing [%s:%d] : '%s': %s.\n", file, linenum, args[0], errmsg);
 				err_code |= ERR_ALERT | ERR_FATAL;
diff --git a/src/http_act.c b/src/http_act.c
index 4c0c5c406..718501416 100644
--- a/src/http_act.c
+++ b/src/http_act.c
@@ -558,7 +558,7 @@ static enum act_parse_ret parse_http_req_capture(const char **args, int *orig_ar
 	}
 
 	cur_arg = *orig_arg;
-	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args);
+	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args, NULL);
 	if (!expr)
 		return ACT_RET_PRS_ERR;
 
@@ -743,7 +743,7 @@ static enum act_parse_ret parse_http_res_capture(const char **args, int *orig_ar
 	}
 
 	cur_arg = *orig_arg;
-	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args);
+	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args, NULL);
 	if (!expr)
 		return ACT_RET_PRS_ERR;
 
@@ -1730,7 +1730,7 @@ static enum act_parse_ret parse_http_track_sc(const char **args, int *orig_arg,
 
 	cur_arg = *orig_arg;
 	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line,
-				 err, &px->conf.args);
+				 err, &px->conf.args, NULL);
 	if (!expr)
 		return ACT_RET_PRS_ERR;
 
diff --git a/src/log.c b/src/log.c
index 23e6c4757..51d684d6e 100644
--- a/src/log.c
+++ b/src/log.c
@@ -488,7 +488,7 @@ int add_sample_to_logformat_list(char *text, char *arg, int arg_len, struct prox
 	cmd[1] = "";
 	cmd_arg = 0;
 
-	expr = sample_parse_expr(cmd, &cmd_arg, curpx->conf.args.file, curpx->conf.args.line, err, &curpx->conf.args);
+	expr = sample_parse_expr(cmd, &cmd_arg, curpx->conf.args.file, curpx->conf.args.line, err, &curpx->conf.args, NULL);
 	if (!expr) {
 		memprintf(err, "failed to parse sample expression <%s> : %s", text, *err);
 		goto error_free;
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 7668ec29c..8486863a2 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -1287,7 +1287,7 @@ enum act_parse_ret tcp_parse_set_src_dst(const char **args, int *orig_arg, struc
 	unsigned int where;
 
 	cur_arg = *orig_arg;
-	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args);
+	expr = sample_parse_expr((char **)args, &cur_arg, px->conf.args.file, px->conf.args.line, err, &px->conf.args, NULL);
 	if (!expr)
 		return ACT_RET_PRS_ERR;
 
diff --git a/src/queue.c b/src/queue.c
index 1bb08a513..9fd3e9d15 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -544,7 +544,7 @@ static enum act_parse_ret parse_set_priority_class(const char **args, int *arg,
 	unsigned int where = 0;
 
 	rule->arg.expr = sample_parse_expr((char **)args, arg, px->conf.args.file,
-	                                   px->conf.args.line, err, &px->conf.args);
+	                                   px->conf.args.line, err, &px->conf.args, NULL);
 	if (!rule->arg.expr)
 		return ACT_RET_PRS_ERR;
 
@@ -572,7 +572,7 @@ static enum act_parse_ret parse_set_priority_offset(const char **args, int *arg,
 	unsigned int where = 0;
 
 	rule->arg.expr = sample_parse_expr((char **)args, arg, px->conf.args.file,
-	                                   px->conf.args.line, err, &px->conf.args);
+	                                   px->conf.args.line, err, &px->conf.args, NULL);
 	if (!rule->arg.expr)
 		return ACT_RET_PRS_ERR;
 
diff --git a/src/sample.c b/src/sample.c
index d82451fc3..ef0f7b00c 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -824,8 +824,11 @@ sample_cast_fct sample_casts[SMP_TYPES][SMP_TYPES] = {
  *        fetch keyword followed by format conversion keywords.
  * Returns a pointer on allocated sample expression structure.
  * The caller must have set al->ctx.
+ * If <endptr> is non-nul, it will be set to the first unparsed character
+ * (which may be the final '\0') on success. If it is nul, the expression
+ * must be properly terminated by a '\0' otherwise an error is reported.
  */
-struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, int line, char **err_msg, struct arg_list *al)
+struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, int line, char **err_msg, struct arg_list *al, char **endptr)
 {
 	const char *begw; /* beginning of word */
 	const char *endw; /* end of word */
@@ -917,6 +920,10 @@ struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, in
 		int argcnt;
 
 		if (*endt && *endt != ',') {
+			if (endptr) {
+				/* end found, let's stop here */
+				break;
+			}
 			if (ckw)
 				memprintf(err_msg, "missing comma after converter '%s'", ckw);
 			else
@@ -949,8 +956,10 @@ struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, in
 		conv = find_sample_conv(begw, endw - begw);
 		if (!conv) {
 			/* we found an isolated keyword that we don't know, it's not ours */
-			if (begw == str[*idx])
+			if (begw == str[*idx]) {
+				endt = begw;
 				break;
+			}
 			memprintf(err_msg, "unknown converter '%s'", ckw);
 			goto out_error;
 		}
@@ -996,6 +1005,11 @@ struct sample_expr *sample_parse_expr(char **str, int *idx, const char *file, in
 		}
 	}
 
+	if (endptr) {
+		/* end found, let's stop here */
+		*endptr = (char *)endt;
+	}
+
  out:
 	free(fkw);
 	free(ckw);
diff --git a/src/server.c b/src/server.c
index d7cb97d9a..959fb22e7 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1538,7 +1538,7 @@ static struct sample_expr *srv_sni_sample_parse_expr(struct server *srv, struct
 	idx = 0;
 	px->conf.args.ctx = ARGC_SRV;
 
-	return sample_parse_expr((char **)args, &idx, file, linenum, err, &px->conf.args);
+	return sample_parse_expr((char **)args, &idx, file, linenum, err, &px->conf.args, NULL);
 }
 
 static int server_parse_sni_expr(struct server *newsrv, struct proxy *px, char **err)
diff --git a/src/stick_table.c b/src/stick_table.c
index 1e7d4f3a8..9937f115f 100644
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -2118,7 +2118,7 @@ static enum act_parse_ret parse_set_gpt0(const char **args, int *arg, struct pro
 	rule->arg.gpt.value = strtol(args[*arg], &error, 10);
 	if (*error != '\0') {
 		rule->arg.gpt.expr = sample_parse_expr((char **)args, arg, px->conf.args.file,
-		                                       px->conf.args.line, err, &px->conf.args);
+		                                       px->conf.args.line, err, &px->conf.args, NULL);
 		if (!rule->arg.gpt.expr)
 			return ACT_RET_PRS_ERR;
 
diff --git a/src/tcp_rules.c b/src/tcp_rules.c
index 7eb565914..fc8b4aed9 100644
--- a/src/tcp_rules.c
+++ b/src/tcp_rules.c
@@ -766,7 +766,7 @@ static int tcp_parse_request_rule(char **args, int arg, int section_type,
 		arg++;
 
 		curpx->conf.args.ctx = ARGC_CAP;
-		expr = sample_parse_expr(args, &arg, file, line, err, &curpx->conf.args);
+		expr = sample_parse_expr(args, &arg, file, line, err, &curpx->conf.args, NULL);
 		if (!expr) {
 			memprintf(err,
 			          "'%s %s %s' : %s",
@@ -847,7 +847,7 @@ static int tcp_parse_request_rule(char **args, int arg, int section_type,
 		}
 
 		curpx->conf.args.ctx = ARGC_TRK;
-		expr = sample_parse_expr(args, &arg, file, line, err, &curpx->conf.args);
+		expr = sample_parse_expr(args, &arg, file, line, err, &curpx->conf.args, NULL);
 		if (!expr) {
 			memprintf(err,
 			          "'%s %s %s' : %s",
diff --git a/src/vars.c b/src/vars.c
index ff6baf5dc..63e210331 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -749,7 +749,7 @@ static enum act_parse_ret parse_store(const char **args, int *arg, struct proxy
 	kw_name = args[*arg-1];
 
 	rule->arg.vars.expr = sample_parse_expr((char **)args, arg, px->conf.args.file,
-	                                        px->conf.args.line, err, &px->conf.args);
+	                                        px->conf.args.line, err, &px->conf.args, NULL);
 	if (!rule->arg.vars.expr)
 		return ACT_RET_PRS_ERR;