diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index d6a90b8..e0457ae 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -6318,7 +6318,7 @@
         view, (PyObject*)self, (void *)self->buffer, 4, 1, flags);
 }
 
-static int
+static void
 heapctypewithbuffer_releasebuffer(HeapCTypeWithBufferObject *self, Py_buffer *view)
 {
     assert(view->obj == (void*) self);