diff --git a/python/descriptor_pool.c b/python/descriptor_pool.c
index 073fbda..f6083f7 100644
--- a/python/descriptor_pool.c
+++ b/python/descriptor_pool.c
@@ -45,7 +45,7 @@
   PyObject* db;  // The DescriptorDatabase underlying this pool.  May be NULL.
 } PyUpb_DescriptorPool;
 
-PyObject* PyUpb_DescriptorPool_GetDefaultPool() {
+PyObject* PyUpb_DescriptorPool_GetDefaultPool(void) {
   PyUpb_ModuleState* s = PyUpb_ModuleState_Get();
   return s->default_pool;
 }