diff --git a/src/snmalloc/override/malloc-extensions.h b/src/snmalloc/override/malloc-extensions.h
index 2fc6777..f7429cd 100644
--- a/src/snmalloc/override/malloc-extensions.h
+++ b/src/snmalloc/override/malloc-extensions.h
@@ -1,3 +1,4 @@
+#pragma once
 /**
  * Malloc extensions
  *