diff --git a/text.cpp b/text.cpp
index 73caf87..6bc7d04 100644
--- a/text.cpp
+++ b/text.cpp
@@ -7,6 +7,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdarg.h>
 
 /**
  * Returns an empty string if `s` is valid utf8;