diff --git a/synapse/http/request_metrics.py b/synapse/http/request_metrics.py
index 284d5e05d..72c265467 100644
--- a/synapse/http/request_metrics.py
+++ b/synapse/http/request_metrics.py
@@ -113,7 +113,7 @@ in_flight_requests_db_sched_duration = Counter(
 _in_flight_requests = set()
 
 # Protects the _in_flight_requests set from concurrent accesss
-_in_flight_reqeuests_lock = threading.Lock()
+_in_flight_requests_lock = threading.Lock()
 
 
 def _get_in_flight_counts():
@@ -124,7 +124,7 @@ def _get_in_flight_counts():
     """
     # Cast to a list to prevent it changing while the Prometheus
     # thread is collecting metrics
-    with _in_flight_reqeuests_lock:
+    with _in_flight_requests_lock:
         reqs = list(_in_flight_requests)
 
     for rm in reqs:
@@ -159,11 +159,11 @@ class RequestMetrics(object):
         # to the "in flight" metrics.
         self._request_stats = self.start_context.get_resource_usage()
 
-        with _in_flight_reqeuests_lock:
+        with _in_flight_requests_lock:
             _in_flight_requests.add(self)
 
     def stop(self, time_sec, request):
-        with _in_flight_reqeuests_lock:
+        with _in_flight_requests_lock:
             _in_flight_requests.discard(self)
 
         context = LoggingContext.current_context()