diff --git a/swh/core/api/asynchronous.py b/swh/core/api/asynchronous.py
--- a/swh/core/api/asynchronous.py
+++ b/swh/core/api/asynchronous.py
@@ -22,7 +22,8 @@
 def decode_request(request):
     content_type = request.headers.get('Content-Type')
     data = yield from request.read()
-
+    if not data:
+        return {}
     if content_type == 'application/x-msgpack':
         r = msgpack_loads(data)
     elif content_type == 'application/json':
diff --git a/swh/core/db/__init__.py b/swh/core/db/__init__.py
--- a/swh/core/db/__init__.py
+++ b/swh/core/db/__init__.py
@@ -92,7 +92,7 @@
         if self.pool:
             self.pool.putconn(self.conn)
 
-    def cursor(self, cur_arg):
+    def cursor(self, cur_arg=None):
         """get a cursor: from cur_arg if given, or a fresh one otherwise
 
         meant to avoid boilerplate if/then/else in methods that proxy stored