diff --git a/src/tree_schema_free.c b/src/tree_schema_free.c
index eb3c563..fdb0bd5 100644
--- a/src/tree_schema_free.c
+++ b/src/tree_schema_free.c
@@ -1041,7 +1041,7 @@
     free(module);
 }
 
-API void
+LIBYANG_API_DEF void
 lyplg_ext_instance_substatements_free(struct ly_ctx *ctx, struct lysc_ext_substmt *substmts)
 {
     LY_ARRAY_COUNT_TYPE u;