diff --git a/src/typval.c b/src/typval.c
index 01ffef5..e57d898 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -1021,7 +1021,7 @@
 /*
  * Returns TRUE if "tv" is a type alias for a class
  */
-    int
+    static int
 tv_class_alias(typval_T *tv)
 {
     return tv->v_type == VAR_TYPEALIAS &&