diff --git a/requests/hooks.py b/requests/hooks.py
index 13d0eb5c..272abb73 100644
--- a/requests/hooks.py
+++ b/requests/hooks.py
@@ -30,7 +30,6 @@ import traceback
 
 HOOKS = ('args', 'pre_request', 'pre_send', 'post_request', 'response')
 
-
 def dispatch_hook(key, hooks, hook_data):
     """Dispatches a hook dictionary on a given piece of data."""
 
@@ -44,7 +43,10 @@ def dispatch_hook(key, hooks, hook_data):
 
         for hook in hooks:
             try:
-                hook_data = hook(hook_data) or hook_data
+                _hook_data = hook(hook_data)
+                if _hook_data is not None:
+                    hook_data = _hook_data
+
             except Exception:
                 traceback.print_exc()