diff --git a/addons/promex/service-prometheus.c b/addons/promex/service-prometheus.c
index 0cd5a6c0f..a09fa8730 100644
--- a/addons/promex/service-prometheus.c
+++ b/addons/promex/service-prometheus.c
@@ -36,6 +36,7 @@
 #include <haproxy/stats.h>
 #include <haproxy/stconn.h>
 #include <haproxy/stream.h>
+#include <haproxy/stress.h>
 #include <haproxy/task.h>
 #include <haproxy/tools.h>
 #include <haproxy/version.h>
@@ -347,6 +348,10 @@ static int promex_dump_ts(struct appctx *appctx, struct ist prefix,
 	istcat(&n, prefix, PROMEX_MAX_NAME_LEN);
 	istcat(&n, name, PROMEX_MAX_NAME_LEN);
 
+	/* In stress mode, force yielding on each metric. */
+	if (STRESS_RUN1(istlen(*out), 0))
+		goto full;
+
 	if ((ctx->flags & PROMEX_FL_METRIC_HDR) &&
 	    !promex_dump_ts_header(n, desc, type, out, max))
 		goto full;