diff --git a/swh/objstorage/backends/azure.py b/swh/objstorage/backends/azure.py
index be7aeaa..80d8fba 100644
--- a/swh/objstorage/backends/azure.py
+++ b/swh/objstorage/backends/azure.py
@@ -78,12 +78,23 @@ def get_container_url(
 
 def call_async(f, *args):
     """Calls an async coroutine from a synchronous function."""
+    # if called from another async function (eg. gunicorn), we need to temporarily
+    # disable it.
+    # FIXME: the right fix would be either:
+    #   * to use async in the whole stack, or
+    #   * use a threaded server instead of an async server
+    # because doing it this way blocks the whole server while serving the request.
+    parent_loop = asyncio.events._get_running_loop()
+    asyncio.events._set_running_loop(None)
+
     loop = asyncio.new_event_loop()
+    assert asyncio.events._get_running_loop() is None
     try:
         return loop.run_until_complete(f(*args))
     finally:
         loop.run_until_complete(loop.shutdown_asyncgens())
         loop.close()
+        asyncio.events._set_running_loop(parent_loop)
 
 
 class AzureCloudObjStorage(ObjStorage):