diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index d89b14e..52812ea 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -1636,6 +1636,28 @@
   END
   v9.CheckScriptSuccess(lines)
   unlet g:result
+
+  # Using super, Child invokes Base method which has optional arg. #12471
+  lines =<< trim END
+    vim9script
+
+    class Base
+        this.success: bool = false
+        def Method(arg = 0)
+            this.success = true
+        enddef
+    endclass
+
+    class Child extends Base
+        def new()
+            super.Method()
+        enddef
+    endclass
+
+    var obj = Child.new()
+    assert_equal(true, obj.success)
+  END
+  v9.CheckScriptSuccess(lines)
 enddef
 
 
diff --git a/src/userfunc.c b/src/userfunc.c
index c30c352..8facd2f 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -5651,8 +5651,8 @@
     //    type_T	**uf_arg_types;
     //    type_T	*uf_ret_type;
 
-    ufunc->uf_type_list.ga_len = 0;
-    ufunc->uf_type_list.ga_data = NULL;
+    // make uf_type_list empty
+    ga_init(&ufunc->uf_type_list);
 
     // TODO:   partial_T	*uf_partial;
 
diff --git a/src/version.c b/src/version.c
index c9a4feb..335e3bd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1605,
+/**/
     1604,
 /**/
     1603,
diff --git a/src/vim9class.c b/src/vim9class.c
index 062de8f..734967a 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -1025,7 +1025,9 @@
 	    if (*fup == NULL)
 		goto cleanup;
 
-	    mch_memmove(*fup, gap->ga_data, sizeof(ufunc_T *) * gap->ga_len);
+	    if (gap->ga_len != 0)
+		mch_memmove(*fup, gap->ga_data,
+					      sizeof(ufunc_T *) * gap->ga_len);
 	    vim_free(gap->ga_data);
 	    if (loop == 1)
 		cl->class_class_function_count_child = gap->ga_len;