diff --git a/modules/modhelp.py b/modules/modhelp.py
index 5d8f89b31bc..445cb3b1d09 100755
--- a/modules/modhelp.py
+++ b/modules/modhelp.py
@@ -154,7 +154,7 @@ def main():
 int plugin_is_GPL_compatible;
 
 static emacs_value
-${c_func} (emacs_env *env, int nargs, emacs_value args[], void *data)
+${c_func} (emacs_env *env, ptrdiff_t nargs, emacs_value args[], void *data)
 {
   return env->intern (env, "t");
 }