diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
index cf4e854d829..e6910b3083a 100644
--- a/Python/thread_pthread.h
+++ b/Python/thread_pthread.h
@@ -134,7 +134,7 @@ do { \
 static pthread_condattr_t *condattr_monotonic = NULL;
 
 static void
-init_condattr()
+init_condattr(void)
 {
 #ifdef CONDATTR_MONOTONIC
     static pthread_condattr_t ca;