diff --git a/flask_restful/reqparse.py b/flask_restful/reqparse.py
index 9bb30991..36a6362d 100644
--- a/flask_restful/reqparse.py
+++ b/flask_restful/reqparse.py
@@ -122,6 +122,8 @@ def source(self, request):
         else:
             values = MultiDict()
             for l in self.location:
+                if not request.is_json and l == 'json':
+                    continue
                 value = getattr(request, l, None)
                 if callable(value):
                     value = value()