diff --git a/sat_solver.cpp b/sat_solver.cpp
index e191881..07c0926 100644
--- a/sat_solver.cpp
+++ b/sat_solver2.cpp
@@ -43,6 +43,7 @@
 #include <vector>
 #include <dirent.h>
 #include "SAT.h"
+#include <cstring>
 
 using namespace std;