diff --git a/src/level_set/redistancing_Sussman/HelpFunctions.hpp b/src/level_set/redistancing_Sussman/HelpFunctions.hpp
index 10174340b6d60a878e95ad063410448800ea04c8..bef0601391cca65739ab1b16267a198257e1452d 100644
--- a/src/level_set/redistancing_Sussman/HelpFunctions.hpp
+++ b/src/level_set/redistancing_Sussman/HelpFunctions.hpp
@@ -13,6 +13,7 @@
 #define REDISTANCING_SUSSMAN_HELPFUNCTIONS_HPP
 
 #include <iostream>
+#include <fstream>
 /**@brief Gets the sign of a variable.
  *
  * @tparam T Inferred type of input variable.