diff --git a/third_party/vaca/src/Debug.cpp b/third_party/vaca/src/Debug.cpp
index 23f908083..a250a9bfc 100644
--- a/third_party/vaca/src/Debug.cpp
+++ b/third_party/vaca/src/Debug.cpp
@@ -36,6 +36,7 @@
 // #include "Vaca/Thread.h"
 
 #include <cstdio>
+#include <cstdarg>
 
 using namespace std;
 using namespace Vaca;