diff --git a/osbuild/sources.py b/osbuild/sources.py
index 9e9cd574..78c72858 100644
--- a/osbuild/sources.py
+++ b/osbuild/sources.py
@@ -14,9 +14,9 @@ class SourcesServer:
         self.output = output
         self.options = options or {}
         self.secrets = secrets or {}
-        self.event_loop = asyncio.new_event_loop()
-        self.thread = threading.Thread(target=self._run_event_loop)
         self.barrier = threading.Barrier(2)
+        self.event_loop = None
+        self.thread = None
 
     def _run_source(self, source, checksums):
         msg = {
@@ -53,13 +53,25 @@ class SourcesServer:
             self.event_loop.remove_reader(server)
 
     def __enter__(self):
+        # We are not re-entrant, so complain if re-entered.
+        assert self.event_loop is None
+
+        self.event_loop = asyncio.new_event_loop()
+        self.thread = threading.Thread(target=self._run_event_loop)
+
+        self.barrier.reset()
         self.thread.start()
         self.barrier.wait()
+
         return self
 
     def __exit__(self, *args):
         self.event_loop.call_soon_threadsafe(self.event_loop.stop)
         self.thread.join()
+        self.event_loop.close()
+
+        self.thread = None
+        self.event_loop = None
 
 
 def get(source, checksums, api_path="/run/osbuild/api/sources"):