diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index c552337..60de8b4 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -1214,7 +1214,7 @@
 	struct field metric;
 	struct channel *chn = si_ic(appctx->owner);
 	struct ist out = ist2(trash.area, 0);
-	size_t max = channel_htx_recv_max(chn, htx);
+	size_t max = htx_free_data_space(htx);
 	int ret = 1;
 
 #ifdef USE_OPENSSL
@@ -1427,7 +1427,7 @@
 	struct field metric;
 	struct channel *chn = si_ic(appctx->owner);
 	struct ist out = ist2(trash.area, 0);
-	size_t max = channel_htx_recv_max(chn, htx);
+	size_t max = htx_free_data_space(htx);
 	int ret = 1;
 
 	while (appctx->st2 && appctx->st2 < ST_F_TOTAL_FIELDS) {
@@ -1605,7 +1605,7 @@
 	struct field metric;
 	struct channel *chn = si_ic(appctx->owner);
 	struct ist out = ist2(trash.area, 0);
-	size_t max = channel_htx_recv_max(chn, htx);
+	size_t max = htx_free_data_space(htx);
 	int ret = 1;
 	uint32_t weight;
 
@@ -1824,7 +1824,7 @@
 	struct field metric;
 	struct channel *chn = si_ic(appctx->owner);
 	struct ist out = ist2(trash.area, 0);
-	size_t max = channel_htx_recv_max(chn, htx);
+	size_t max = htx_free_data_space(htx);
 	int ret = 1;
 	uint32_t weight;