diff --git a/changelog.d/19383.misc b/changelog.d/19383.misc
new file mode 100644
index 0000000000..4749b1af9a
--- /dev/null
+++ b/changelog.d/19383.misc
@@ -0,0 +1 @@
+Warn about skipping reactor metrics when using unknown reactor type.
diff --git a/synapse/metrics/_reactor_metrics.py b/synapse/metrics/_reactor_metrics.py
index 9852d0b932..e73ade9890 100644
--- a/synapse/metrics/_reactor_metrics.py
+++ b/synapse/metrics/_reactor_metrics.py
@@ -158,12 +158,17 @@ try:
         else:
             # E.g. this does not support the (Windows-only) ProactorEventLoop.
             logger.warning(
-                "Skipping configuring ReactorLastSeenMetric: unexpected asyncio loop selector: %r via %r",
+                "Skipping configuring reactor metrics: unexpected asyncio loop selector: %r via %r",
                 selector,
                 asyncio_loop,
             )
+    else:
+        logger.warning(
+            "Skipping configuring reactor metrics: unexpected reactor type: %r",
+            reactor,
+        )
 except Exception as e:
-    logger.warning("Configuring ReactorLastSeenMetric failed: %r", e)
+    logger.warning("Configuring reactor metrics failed: %r", e)
 
 
 if wrapper: