diff --git a/RaspberryPi/calculate.h b/RaspberryPi/calculate.h
index e62bd13..dfb49ec 100644
--- a/RaspberryPi/calculate.h
+++ b/RaspberryPi/calculate.h
@@ -1,4 +1,8 @@
-/* Include guard */
+#ifndef dht22_H
+#define dht22_H
+
 #include "dht22.h"
 
 double absoluteHumidity(sensor *sensor);
+
+#endif
\ No newline at end of file