diff --git a/Qk.h b/Qk.h
index 326a342..6733693 100644
--- a/Qk.h
+++ b/Qk.h
@@ -1,3 +1,8 @@
+#ifndef QK_H
+#define QK_H
+
+#include <cstdio>
+
 double TauCal(double Energy_MeV){
 
   double E_log = log(Energy_MeV);
@@ -247,3 +252,5 @@ double QK2(double Energy, double radius, double distance, double thickness){
   */
   return QD2;
 }
+
+#endif