diff --git a/test/unit/radix_tree_t.c b/test/unit/radix_tree_t.c
index 6a7ecac6f..4455f2b04 100644
--- a/test/unit/radix_tree_t.c
+++ b/test/unit/radix_tree_t.c
@@ -19,7 +19,7 @@
 
 //----------------------------------------------------------------
 
-static void *rt_init()
+static void *rt_init(void)
 {
 	struct radix_tree *rt = radix_tree_create();
 	T_ASSERT(rt);