diff --git a/django/contrib/admin/views/doc.py b/django/contrib/admin/views/doc.py
index 560552e1d5..e060e53867 100644
--- a/django/contrib/admin/views/doc.py
+++ b/django/contrib/admin/views/doc.py
@@ -185,7 +185,7 @@ def model_detail(request, app_label, model_name):
 
     # Gather model methods.
     for func_name, func in model.__dict__.items():
-        if (inspect.isfunction(func) or inspect.ismethod(func)) and len(inspect.getargspec(func)[0]) == 0:
+        if (inspect.isfunction(func) and len(inspect.getargspec(func)[0]) == 1):
             try:
                 for exclude in MODEL_METHODS_EXCLUDE:
                     if func_name.startswith(exclude):