diff --git a/include/xsimd/stl/algorithms.hpp b/include/xsimd/stl/algorithms.hpp
index 4cb2b79..1590b89 100644
--- a/include/xsimd/stl/algorithms.hpp
+++ b/include/xsimd/stl/algorithms.hpp
@@ -6,6 +6,9 @@
 * The full license is in the file LICENSE, distributed with this software. *
 ****************************************************************************/
 
+#ifndef XSIMD_ALGORITHMS_HPP
+#define XSIMD_ALGORITHMS_HPP
+
 #include "xsimd/memory/xsimd_load_store.hpp"
 
 namespace xsimd
@@ -126,4 +129,6 @@ namespace xsimd
 
         #undef XSIMD_LOOP_MACRO
     }
-}
\ No newline at end of file
+}
+
+#endif
\ No newline at end of file