diff --git a/src/math/interval/mod_interval.h b/src/math/interval/mod_interval.h
index 88acdd8d6..ed189fe7b 100644
--- a/src/math/interval/mod_interval.h
+++ b/src/math/interval/mod_interval.h
@@ -15,6 +15,8 @@ Author:
 
 --*/
 
+#pragma once
+
 namespace bv {
 
     template<typename T, typename Base>