diff --git a/tox.ini b/tox.ini
index 6bb632b..25736ee 100644
--- a/tox.ini
+++ b/tox.ini
@@ -87,5 +87,5 @@ deps=
 commands=
     {envbindir}/coverage erase
     {envbindir}/coverage combine
-    {envbindir}/coverage xml wsme/*.py wsme/protocols/*.py
+    {envbindir}/coverage xml wsme/*.py wsme/rest/*.py
     {envbindir}/coverage report --show-missing wsme/*.py wsme/protocols/*.py
diff --git a/wsme/rest/args.py b/wsme/rest/args.py
index 85c0fe7..a68849e 100644
--- a/wsme/rest/args.py
+++ b/wsme/rest/args.py
@@ -153,6 +153,8 @@ def args_from_body(funcdef, body, mimetype):
         dataformat = restjson
     elif mimetype in restxml.accept_content_types:
         dataformat = restxml
+    elif not body:
+        return (), {}
     else:
         raise ValueError("Unknow mimetype: %s" % mimetype)