diff --git a/shtab/__init__.py b/shtab/__init__.py
index 3564fb9..5a6c63c 100644
--- a/shtab/__init__.py
+++ b/shtab/__init__.py
@@ -537,7 +537,7 @@ def recurse(parser, prefix, paths=None):
                         format_positional(opt) for opt in subparser._get_positional_actions()
                         if not isinstance(opt.choices, dict) if opt.help != SUPPRESS)
 
-                    new_pref = prefix + "_" + wordify(cmd)
+                    new_pref = f"{prefix}_{wordify(cmd)}"
                     options = all_commands[new_pref] = {
                         "cmd": cmd, "help": (subparser.description or "").strip().split("\n")[0],
                         "arguments": arguments, "paths": [*paths, cmd]}
@@ -655,7 +655,10 @@ def complete_tcsh(parser, root_prefix=None, preamble="", choice_functions=None):
     """
     Return tcsh syntax autocompletion script.
 
-    See `complete` for arguments.
+    root_prefix:
+      ignored (tcsh has no support for functions)
+
+    See `complete` for other arguments.
     """
     optionals_single = set()
     optionals_double = set()
@@ -716,17 +719,22 @@ def recurse_parser(cparser, positional_idx, requirements=None):
             # Multiple requirements
             nlist = []
             for nn, arg in ndict.items():
-                checks = [f'[ "$cmd[{iidx}]" == "{n}" ]' for iidx, n in enumerate(nn, start=2)]
                 if arg.choices:
-                    nlist.append('( {}echo "{}" || false )'.format(
-                        ' && '.join(checks + ['']),                 # Append the separator
-                        '\\n'.join(arg.choices),
-                    ))
-
+                    checks = [f'[ "$cmd[{iidx}]" == "{n}" ]' for iidx, n in enumerate(nn, start=2)]
+                    choices_str = "' '".join(arg.choices)
+                    checks_str = ' && '.join(checks + [f"echo '{choices_str}'"])
+                    nlist.append(f"( {checks_str} || false )")
             # Ugly hack
             nlist_str = ' || '.join(nlist)
             specials.append(f"'p@{str(idx)}@`set cmd=($COMMAND_LINE); {nlist_str}`@'")
 
+    if optionals_double:
+        if optionals_single:
+            optionals_single.add('-')
+        else:
+            # Don't add a space after completing "--" from "-"
+            optionals_single = ('-', '-')
+
     return Template("""\
 # AUTOMATICALLY GENERATED by `shtab`
 
@@ -734,13 +742,13 @@ def recurse_parser(cparser, positional_idx, requirements=None):
 
 complete ${prog} \\
         'c/--/(${optionals_double_str})/' \\
-        'c/-/(${optionals_single_str} -)/' \\
+        'c/-/(${optionals_single_str})/' \\
         ${optionals_special_str} \\
         'p/*/()/'""").safe_substitute(
         preamble=("\n# Custom Preamble\n" + preamble +
                   "\n# End Custom Preamble\n" if preamble else ""), root_prefix=root_prefix,
-        prog=parser.prog, optionals_double_str=' '.join(optionals_double),
-        optionals_single_str=' '.join(optionals_single),
+        prog=parser.prog, optionals_double_str=' '.join(sorted(optionals_double)),
+        optionals_single_str=' '.join(sorted(optionals_single)),
         optionals_special_str=' \\\n        '.join(specials))