diff --git a/src/schema_compile.c b/src/schema_compile.c
index 3588a7d..d725efb 100644
--- a/src/schema_compile.c
+++ b/src/schema_compile.c
@@ -143,7 +143,7 @@
     return orig;
 }
 
-LY_ERR
+API LY_ERR
 lysc_ext_substmt(const struct lysc_ext_instance *ext, enum ly_stmt substmt, void **instance_p, enum ly_stmt_cardinality *cardinality_p)
 {
     LY_ARRAY_COUNT_TYPE u;