diff --git a/conda/cli/conda_argparse.py b/conda/cli/conda_argparse.py
index b4279c719e2..1394248f7ef 100644
--- a/conda/cli/conda_argparse.py
+++ b/conda/cli/conda_argparse.py
@@ -21,6 +21,7 @@
 
 from .. import __version__
 from ..auxlib.ish import dals
+from ..auxlib.compat import isiterable
 from ..base.constants import COMPATIBLE_SHELLS, CONDA_HOMEPAGE_URL, DepsModifier, \
     UpdateModifier, ExperimentalSolverChoice
 from ..common.constants import NULL
@@ -173,6 +174,14 @@ def print_help(self):
                 builder.extend('  %s' % cmd for cmd in sorted(other_commands))
                 print('\n'.join(builder))
 
+    def _check_value(self, action, value):
+        # extend to properly handle when we accept multiple choices and the default is a list
+        if action.choices is not None and isiterable(value):
+            for element in value:
+                super()._check_value(action, element)
+        else:
+            super()._check_value(action, value)
+
 
 def _exec(executable_args, env_vars):
     return (_exec_win if on_win else _exec_unix)(executable_args, env_vars)
@@ -723,10 +732,14 @@ def configure_parser_init(sub_parsers):
     p.add_argument(
         'shells',
         nargs='*',
-        help="One or more shells to be initialized. If not given, the default value is "
-             "'bash' on unix and 'cmd.exe' on Windows. Use the '--all' flag to initialize "
-             "all shells. Currently compatible shells are {%s}."
-             % ", ".join(sorted(COMPATIBLE_SHELLS)),
+        choices=COMPATIBLE_SHELLS,
+        metavar="SHELLS",
+        help=(
+            "One or more shells to be initialized. If not given, the default value is 'bash' on "
+            "unix and 'cmd.exe' & 'powershell' on Windows. Use the '--all' flag to initialize all "
+            f"shells. Available shells: {sorted(COMPATIBLE_SHELLS)}"
+        ),
+        default=["cmd.exe", "powershell"] if on_win else ["bash"],
     )
 
     if on_win:
diff --git a/conda/cli/main_init.py b/conda/cli/main_init.py
index e6b5d1eeb8b..91a37768dfb 100644
--- a/conda/cli/main_init.py
+++ b/conda/cli/main_init.py
@@ -7,6 +7,7 @@
 
 from ..base.context import context
 from ..common.compat import on_win
+from ..exceptions import ArgumentError
 
 log = getLogger(__name__)
 
@@ -18,26 +19,15 @@ def execute(args, parser):
     if args.install:
         return install(context.conda_prefix)
 
-    invalid_shells = tuple(s for s in args.shells if s not in COMPATIBLE_SHELLS)
-    if invalid_shells:
-        from ..exceptions import ArgumentError
-        from ..common.io import dashlist
-        raise ArgumentError("Invalid shells: %s\n\n"
-                            "Currently available shells are:%s"
-                            % (dashlist(invalid_shells), dashlist(sorted(COMPATIBLE_SHELLS))))
-
     if args.all:
         selected_shells = COMPATIBLE_SHELLS
     else:
         selected_shells = tuple(args.shells)
 
-    if not selected_shells:
-        selected_shells = ('cmd.exe', 'powershell') if on_win else ('bash',)
-
     if args.dev:
-        assert len(selected_shells) == 1, "--dev can only handle one shell at a time right now"
-        shell = selected_shells[0]
-        return initialize_dev(shell)
+        if len(selected_shells) != 1:
+            raise ArgumentError("--dev can only handle one shell at a time right now")
+        return initialize_dev(selected_shells[0])
 
     else:
         for_user = args.user