diff --git a/src/globals.h b/src/globals.h
index bbc12ce..8cc9385 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1699,8 +1699,7 @@
 EXTERN char e_unknown_option[]	INIT(= N_("E113: Unknown option: %s"));
 EXTERN char e_letunexp[]	INIT(= N_("E18: Unexpected characters in :let"));
 EXTERN char e_reduceempty[]	INIT(= N_("E998: Reduce of an empty %s with no initial value"));
-// TODO: Change Error Number
-EXTERN char e_no_dict_key[]	INIT(= N_("E999: Dictionary with key \"%s\" required"));
+EXTERN char e_no_dict_key[]	INIT(= N_("E857: Dictionary key \"%s\" required"));
 #endif
 #ifdef FEAT_QUICKFIX
 EXTERN char e_readerrf[]	INIT(= N_("E47: Error while reading errorfile"));
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index cefeaf7..d0686ef 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1958,6 +1958,7 @@
   let files = readdirex('Xdir2', 1, #{sort: 'none'})->map({-> v:val.name})
   let unsorted = copy(files)
   call assert_equal(['README.txt', 'Readme.txt', 'readme.txt'], sort(files), 'unsorted')
+  call assert_fails("call readdirex('Xdir2', 1, #{slort: 'none'})", 'E857: Dictionary key "sort" required')
 
   " 3) sort by case (same as default)
   let files = readdirex('Xdir2', 1, #{sort: 'case'})->map({-> v:val.name})
diff --git a/src/version.c b/src/version.c
index d69b560..57b092a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    990,
+/**/
     989,
 /**/
     988,