diff --git a/Environment/ShowerAxis.h b/Environment/ShowerAxis.h
index 4b7c273466b6dbc74d3818129b2915f148211303..888f533983a9dfbc1b271c7490f2cd9e37298f5b 100644
--- a/Environment/ShowerAxis.h
+++ b/Environment/ShowerAxis.h
@@ -8,6 +8,7 @@
  * the license.
  */
 
+#pragma once
 #include <corsika/environment/Environment.h>
 #include <corsika/geometry/Point.h>
 #include <corsika/geometry/Vector.h>