diff --git a/lib/adts.h b/lib/adts.h
index 09c99c99..0b7db493 100644
--- a/lib/adts.h
+++ b/lib/adts.h
@@ -1,3 +1,4 @@
+#pragma once
 #include "bitstream.h"
 #include <stdint.h>
 #include <string>