diff --git a/src/textprop.c b/src/textprop.c
index 309f3cb..93787f3 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -668,7 +668,7 @@
 /*
  * Common for f_prop_type_add() and f_prop_type_change().
  */
-    void
+    static void
 prop_type_set(typval_T *argvars, int add)
 {
     char_u	*name;