diff --git a/share/completions/git.fish b/share/completions/git.fish
index 68ecd1268..862f3b579 100644
--- a/share/completions/git.fish
+++ b/share/completions/git.fish
@@ -2565,11 +2565,11 @@ complete -c git -n __fish_git_needs_command -a '(__fish_git_custom_commands)' -d
 function __fish_git_complete_custom_command -a subcommand
     set -l cmd (commandline -xpc)
     set -e cmd[1] # Drop "git".
-    set -lx subcommand_args
+    set -l subcommand_args
     if argparse -s (__fish_git_global_optspecs) -- $cmd
         set subcommand_args $argv[2..] # Drop the subcommand.
     end
-    complete -C "git-$subcommand \$subcommand_args "(commandline -ct)
+    complete -C "git-$subcommand $(string escape -- $subcommand_args) "(commandline -ct)
 end
 
 # source git-* commands' autocompletion file if exists
diff --git a/tests/checks/git.fish b/tests/checks/git.fish
index 2dae920ed..c7b13d5ae 100644
--- a/tests/checks/git.fish
+++ b/tests/checks/git.fish
@@ -40,12 +40,17 @@ echo "echo foo" > git-frobnicate
 chmod +x git-frobnicate
 
 complete -c git-frobnicate -xa 'foo bar baz'
+complete -c git-frobnicate -l onto -xa 'onto1 onto2'
 
 complete -C'git frobnicate '
 #CHECK: bar
 #CHECK: baz
 #CHECK: foo
 
+complete -C'git frobnicate --onto '
+#CHECK: onto1
+#CHECK: onto2
+
 complete -C'git ' | grep '^add'\t
 # (note: actual tab character in the check here)
 #CHECK: add	Add file contents to the staging area