diff --git a/src/complete.h b/src/complete.h
index 2d665879c..2349d1ff1 100644
--- a/src/complete.h
+++ b/src/complete.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <functional>
 #include <vector>
 
 #include "common.h"