diff --git a/mistral/api/controllers/v2/types.py b/mistral/api/controllers/v2/types.py
index 2f0efac5..ca474c2d 100644
--- a/mistral/api/controllers/v2/types.py
+++ b/mistral/api/controllers/v2/types.py
@@ -107,8 +107,12 @@ class JsonType(wtypes.UserType):
         return value
 
     def frombasetype(self, value):
-        # Value must be a string.
-        return json.loads(value) if value is not None else None
+        if isinstance(value, dict):
+            return value
+        try:
+            return json.loads(value) if value is not None else None
+        except TypeError as e:
+            raise ValueError(e)
 
     def tobasetype(self, value):
         # Value must be a dict.
diff --git a/mistral/tests/unit/api/v2/test_action_executions.py b/mistral/tests/unit/api/v2/test_action_executions.py
index 11aa0cb6..259f2771 100644
--- a/mistral/tests/unit/api/v2/test_action_executions.py
+++ b/mistral/tests/unit/api/v2/test_action_executions.py
@@ -197,6 +197,33 @@ class TestActionExecutionsController(base.APITest):
             save_result=True
         )
 
+    @mock.patch.object(rpc.EngineClient, 'start_action')
+    def test_post_json(self, f):
+        f.return_value = ACTION_EX_DB.to_dict()
+
+        resp = self.app.post_json(
+            '/v2/action_executions',
+            {
+                'name': 'std.echo',
+                'input': {},
+                'params': '{"save_result": true}'
+            }
+        )
+
+        self.assertEqual(201, resp.status_int)
+
+        action_exec = ACTION_EX
+        del action_exec['task_name']
+
+        self.assertDictEqual(ACTION_EX, resp.json)
+
+        f.assert_called_once_with(
+            ACTION_EX['name'],
+            json.loads(ACTION_EX['input']),
+            description=None,
+            save_result=True
+        )
+
     @mock.patch.object(rpc.EngineClient, 'start_action')
     def test_post_without_input(self, f):
         f.return_value = ACTION_EX_DB.to_dict()
@@ -230,6 +257,15 @@ class TestActionExecutionsController(base.APITest):
 
         self.assertEqual(400, resp.status_int)
 
+    def test_post_bad_json_input(self):
+        resp = self.app.post_json(
+            '/v2/action_executions',
+            {'input': 2},
+            expect_errors=True
+        )
+
+        self.assertEqual(400, resp.status_int)
+
     @mock.patch.object(rpc.EngineClient, 'on_action_complete')
     def test_put(self, f):
         f.return_value = UPDATED_ACTION_EX_DB