--- prog/checker_string.cpp.orig	2019-10-08 00:15:21 UTC
+++ prog/checker_string.cpp
@@ -6,6 +6,7 @@
 
 #include <assert.h>
 
+#include <assert.h>
 #include "checker_string.hpp"
 #include "speller.hpp"
 #include "document_checker.hpp"
