Index: synapse/pyproject.toml
===================================================================
--- synapse.orig/pyproject.toml
+++ synapse/pyproject.toml
@@ -146,7 +146,7 @@ pymacaroons = ">=0.13.0"
 msgpack = ">=0.5.2"
 phonenumbers = ">=8.2.0"
 # we use GaugeHistogramMetric, which was added in prom-client 0.4.0.
-prometheus-client = ">=0.4.0"
+prometheus-client = ">=0.13.1"
 # we use `order`, which arrived in attrs 19.2.0.
 # Note: 21.1.0 broke `/sync`, see #9936
 attrs = ">=19.2.0,!=21.1.0"