2 files changed, 2 insertions, 2 deletions
diff --git a/src/zix/tree.c b/src/zix/tree.c
index c8a5bb4..dd6be5d 100644
--- a/src/zix/tree.c
+++ b/src/zix/tree.c
@@ -107,7 +107,7 @@ zix_tree_free(ZixTree* t)
 }
 
 size_t
-zix_tree_size(ZixTree* t)
+zix_tree_size(const ZixTree* t)
 {
 	return t->size;
 }
diff --git a/src/zix/tree.h b/src/zix/tree.h
index 5a74fd7..cb8c60d 100644
--- a/src/zix/tree.h
+++ b/src/zix/tree.h
@@ -61,7 +61,7 @@ zix_tree_free(ZixTree* t);
    Return the number of elements in @a t.
 */
 size_t
-zix_tree_size(ZixTree* t);
+zix_tree_size(const ZixTree* t);
 
 /**
    Insert the element @a e into @a t and point @a ti at the new element.