diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
index bda60dd..5be59f4 100644
--- a/Modules/cStringIO.c
+++ b/Modules/cStringIO.c
@@ -639,7 +639,7 @@
 #define DL_EXPORT(RTYPE) RTYPE
 #endif
 DL_EXPORT(void)
-initcStringIO() {
+initcStringIO(void) {
   PyObject *m, *d, *v;