diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index 3071b8f0f..483e7031f 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -1409,7 +1409,7 @@ static int promex_dump_global_metrics(struct appctx *appctx, struct htx *htx)
 	}
 
   end:
-	if (!htx_add_data(htx, out))
+	if (!htx_add_data_atonce(htx, out))
 		return -1; /* Unexpected and unrecoverable error */
 	channel_add_input(chn, out.len);
 	return ret;
@@ -1587,7 +1587,7 @@ static int promex_dump_front_metrics(struct appctx *appctx, struct htx *htx)
 	}
 
   end:
-	if (!htx_add_data(htx, out))
+	if (!htx_add_data_atonce(htx, out))
 		return -1; /* Unexpected and unrecoverable error */
 	channel_add_input(chn, out.len);
 	return ret;
@@ -1805,7 +1805,7 @@ static int promex_dump_back_metrics(struct appctx *appctx, struct htx *htx)
 	}
 
   end:
-	if (!htx_add_data(htx, out))
+	if (!htx_add_data_atonce(htx, out))
 		return -1; /* Unexpected and unrecoverable error */
 	channel_add_input(chn, out.len);
 	return ret;
@@ -1999,7 +1999,7 @@ static int promex_dump_srv_metrics(struct appctx *appctx, struct htx *htx)
 
 
   end:
-	if (!htx_add_data(htx, out))
+	if (!htx_add_data_atonce(htx, out))
 		return -1; /* Unexpected and unrecoverable error */
 	channel_add_input(chn, out.len);
 	return ret;