diff --git a/src/testdir/test_vim9_cmd.vim b/src/testdir/test_vim9_cmd.vim
index a9e10e7..51ae7e6 100644
--- a/src/testdir/test_vim9_cmd.vim
+++ b/src/testdir/test_vim9_cmd.vim
@@ -2036,6 +2036,14 @@
   v9.CheckDefExecAndScriptFailure(lines, 'E486:', 1)
 enddef
 
+def Test_lambda_crash()
+  # This used to crash Vim
+  var lines =<< trim END
+    vim9 () => super      => {
+  END
+  v9.CheckScriptFailureList(lines, ["E1356:", "E1405:"])
+enddef
+
 " Test for the 'previewpopup' option
 def Test_previewpopup()
   set previewpopup=height:10,width:60
@@ -2044,6 +2052,7 @@
   assert_notequal(id, 0)
   assert_match('Xppfile', popup_getoptions(id).title)
   popup_clear()
+  bw Xppfile
   set previewpopup&
 enddef
 
diff --git a/src/version.c b/src/version.c
index 72cce65..e77ef0f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    688,
+/**/
     687,
 /**/
     686,
diff --git a/src/vim9type.c b/src/vim9type.c
index a157121..1f044d3 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -2138,12 +2138,13 @@
     switch (type->tt_type)
     {
 	case VAR_CLASS:
-	    if (IS_ENUM(type->tt_class))
+	    if (type->tt_class != NULL && IS_ENUM(type->tt_class))
 		semsg(_(e_using_enum_as_value_str),
 			type->tt_class->class_name);
 	    else
 		semsg(_(e_using_class_as_value_str),
-			type->tt_class->class_name);
+			type->tt_class == NULL ? (char_u *)""
+			: type->tt_class->class_name);
 	    return FAIL;
 
 	case VAR_TYPEALIAS: