diff --git a/moulinette/core.py b/moulinette/core.py
index 17041253..fa7e3992 100644
--- a/moulinette/core.py
+++ b/moulinette/core.py
@@ -388,6 +388,9 @@ class MoulinetteError(Exception):
         super(MoulinetteError, self).__init__(msg)
         self.strerror = msg
 
+    def content(self):
+        return self.strerror
+
 
 class MoulinetteLdapIsDownError(MoulinetteError):
     """Used when ldap is down"""
diff --git a/moulinette/interfaces/api.py b/moulinette/interfaces/api.py
index 7f679c7d..110150aa 100644
--- a/moulinette/interfaces/api.py
+++ b/moulinette/interfaces/api.py
@@ -481,7 +481,7 @@ class _ActionsMapPlugin(object):
         try:
             ret = self.actionsmap.process(arguments, timeout=30, route=_route)
         except MoulinetteError as e:
-            raise HTTPBadRequestResponse(e.strerror)
+            raise HTTPBadRequestResponse(e)
         except Exception as e:
             if isinstance(e, HTTPResponse):
                 raise e
@@ -550,8 +550,16 @@ class HTTPOKResponse(HTTPResponse):
 
 
 class HTTPBadRequestResponse(HTTPResponse):
-    def __init__(self, output=""):
-        super(HTTPBadRequestResponse, self).__init__(output, 400)
+    def __init__(self, error=""):
+
+        if isinstance(error, MoulinetteError):
+            content = error.content()
+            if isinstance(content, dict):
+                super(HTTPBadRequestResponse, self).__init__(json_encode(content), 400, headers={'Content-type': 'application/json'})
+            else:
+                super(HTTPBadRequestResponse, self).__init__(content, 400)
+        else:
+            super(HTTPBadRequestResponse, self).__init__(error, 400)
 
 
 class HTTPUnauthorizedResponse(HTTPResponse):