diff --git a/src/testdir/test_user_func.vim b/src/testdir/test_user_func.vim
index 747ec48..819a6bb 100644
--- a/src/testdir/test_user_func.vim
+++ b/src/testdir/test_user_func.vim
@@ -434,6 +434,11 @@
   func d.fn()
     return 1
   endfunc
+
+  " cannot delete the dict function by number
+  let nr = substitute(execute('echo d'), '.*function(''\(\d\+\)'').*', '\1', '')
+  call assert_fails('delfunction g:' .. nr, 'E475: Invalid argument: g:')
+
   delfunc d.fn
   call assert_equal({'a' : 10}, d)
 endfunc
diff --git a/src/userfunc.c b/src/userfunc.c
index aa55bc8..e51df51 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -4669,6 +4669,13 @@
     if (eap->nextcmd != NULL)
 	*p = NUL;
 
+    if (isdigit(*name) && fudi.fd_dict == NULL)
+    {
+	if (!eap->skip)
+	    semsg(_(e_invarg2), eap->arg);
+	vim_free(name);
+	return;
+    }
     if (!eap->skip)
 	fp = find_func(name, is_global, NULL);
     vim_free(name);
diff --git a/src/version.c b/src/version.c
index 6301d77..54533dc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3408,
+/**/
     3407,
 /**/
     3406,