diff --git a/buddy.h b/buddy.h
index cdc9502..f31f9b4 100644
--- a/buddy.h
+++ b/buddy.h
@@ -1,3 +1,6 @@
+#ifndef BUDDY_ALLOC_H
+#define BUDDY_ALLOC_H
+
 #include <stddef.h>
 #include <stdint.h>
 #include <stdbool.h>
@@ -126,4 +129,6 @@ bool buddy_owned(struct buddy_alloc *alloc, void *ptr);
  * Returns true if and only if the block at address ptr of size
  * len is owned by the allocator and marked as allocated.
  */
-bool buddy_allocated(struct buddy_alloc *alloc, void *ptr, size_t len);
\ No newline at end of file
+bool buddy_allocated(struct buddy_alloc *alloc, void *ptr, size_t len);
+
+#endif
\ No newline at end of file