diff --git a/test/helpers/tree_helpers.cc b/test/helpers/tree_helpers.cc
index e8b3ace4..fdbcc6db 100644
--- a/test/helpers/tree_helpers.cc
+++ b/test/helpers/tree_helpers.cc
@@ -2,6 +2,7 @@
 #include "helpers/tree_helpers.h"
 #include "helpers/point_helpers.h"
 #include <ostream>
+#include <cstring>
 
 using std::string;
 using std::to_string;