diff --git a/src/lib/forcefield.h b/src/lib/forcefield.h
index 81bd4c1..44761e2 100644
--- a/src/lib/forcefield.h
+++ b/src/lib/forcefield.h
@@ -24,6 +24,7 @@
 #define VINA_FORCEFIELD_H
 
 
+#include <sstream>
 #include <iostream>
 #include <fstream>
 #include <string>