diff --git a/src/labthings_fastapi/server/cli.py b/src/labthings_fastapi/server/cli.py
index 66f854cd..a97c7701 100644
--- a/src/labthings_fastapi/server/cli.py
+++ b/src/labthings_fastapi/server/cli.py
@@ -161,7 +161,7 @@ def serve_from_cli(
         server = ThingServer.from_config(config, True if args.debug else False)
         if dry_run:
             return server
-        uvicorn.run(server.app, host=args.host, port=args.port)
+        uvicorn.run(server.app, host=args.host, port=args.port, ws="websockets-sansio")
     except BaseException as e:
         if args.fallback:
             print(f"Error: {e}")
@@ -174,7 +174,7 @@ def serve_from_cli(
                 )
             )
 
-            uvicorn.run(app, host=args.host, port=args.port)
+            uvicorn.run(app, host=args.host, port=args.port, ws="websockets-sansio")
         else:
             if isinstance(e, (ValidationError, ThingImportFailure)):
                 print(f"Error reading LabThings configuration:\n{e}")
diff --git a/tests/test_fallback.py b/tests/test_fallback.py
index 56a367f1..e3a1136f 100644
--- a/tests/test_fallback.py
+++ b/tests/test_fallback.py
@@ -170,7 +170,7 @@ def test_actual_server_fallback():
 
     # Starting the server is a SystemExit
     with pytest.raises(SystemExit, match="3") as excinfo:
-        uvicorn.run(server.app, port=5000)
+        uvicorn.run(server.app, port=5000, ws="websockets-sansio")
     server_error = excinfo.value
     assert server.startup_failure is not None
     assert server.startup_failure["thing"] == "bad_thing"
diff --git a/tests/test_mjpeg_stream.py b/tests/test_mjpeg_stream.py
index 0effde36..f00b43b1 100644
--- a/tests/test_mjpeg_stream.py
+++ b/tests/test_mjpeg_stream.py
@@ -78,4 +78,4 @@ def test_mjpeg_stream(client):
     assert isinstance(telly, Telly)
     telly.framerate = 6
     telly.frame_limit = -1
-    uvicorn.run(server.app, port=5000)
+    uvicorn.run(server.app, port=5000, ws="websockets-sansio")