diff --git a/juju/client/facade_versions.py b/juju/client/facade_versions.py
index f5c273c2..d595a34b 100644
--- a/juju/client/facade_versions.py
+++ b/juju/client/facade_versions.py
@@ -17,7 +17,7 @@
     'Backups': (3, ),
     'Block': (2, ),
     'Bundle': (6, ),
-    'Charms': (6, ),
+    'Charms': (6, 7),
     'Client': (6, 7, 8),
     'Cloud': (7, ),
     'Controller': (11, 12),
diff --git a/juju/model.py b/juju/model.py
index 2be474d5..b3ea07bb 100644
--- a/juju/model.py
+++ b/juju/model.py
@@ -1,5 +1,6 @@
 # Copyright 2023 Canonical Ltd.
 # Licensed under the Apache V2, see LICENCE file for details.
+from __future__ import annotations
 
 import base64
 import collections
@@ -452,7 +453,7 @@ class LocalDeployType:
     """
 
     async def resolve(self, charm_path, architecture,
-                      app_name=None, channel=None, series=None,
+                      app_name=None, channel=None, series: str|None = None,
                       revision=None, entity_url=None, force=False,
                       model_conf=None):
         """resolve attempts to resolve a local charm or bundle using the url
@@ -1876,7 +1877,7 @@ async def _add_charm(self, charm_url, origin):
         client_facade = client.ClientFacade.from_connection(self.connection())
         return await client_facade.AddCharm(channel=str(origin.risk), url=charm_url, force=False)
 
-    async def _resolve_charm(self, url, origin, force=False, series=None, model_config=None):
+    async def _resolve_charm(self, url, origin, force=False, series: str|None = None, model_config=None):
         """Calls Charms.ResolveCharms to resolve all the fields of the
         charm_origin and also the url and the supported_series
 
@@ -1917,15 +1918,24 @@ async def _resolve_charm(self, url, origin, force=False, series=None, model_conf
         if result.error:
             raise JujuError(f'resolving {url} : {result.error.message}')
 
-        # TODO (cderici) : supported_bases
-        supported_series = result.get('supported_series', result.unknown_fields['supported-series'])
+        charmhub_bases = result.supported_bases
         resolved_origin = result.charm_origin
         charm_url = URL.parse(result.url)
+        if "supported-series" in result.unknown_fields:
+            # Legacy code path for Charms v6, that is Juju < 3.3.0
+            supported_series: list[str] = result.unknown_fields['supported-series']
+            # run the series selector to get a series for the base
+            selected_series = utils.series_selector(series, charm_url, model_config, supported_series, force)
+            result.charm_origin.base = utils.get_base_from_origin_or_channel(resolved_origin, selected_series)
+            charm_url.series = selected_series
 
-        # run the series selector to get a series for the base
-        selected_series = utils.series_selector(series, charm_url, model_config, supported_series, force)
-        result.charm_origin.base = utils.get_base_from_origin_or_channel(resolved_origin, selected_series)
-        charm_url.series = selected_series
+        if series:
+            # Ugh this ugly,
+            # series is valid against Juju 3.0~3.2.x
+            # base is valid against Juju 3.3~4.x
+            # we should convert back and forth really...
+            warnings.warn("series= argument is deprecated, use base= instead", DeprecationWarning, stacklevel=3)
+            # FIXME actually use the argument
 
         return charm_url, resolved_origin
 
diff --git a/juju/utils.py b/juju/utils.py
index c4f4780a..614a9da8 100644
--- a/juju/utils.py
+++ b/juju/utils.py
@@ -1,5 +1,6 @@
 # Copyright 2023 Canonical Ltd.
 # Licensed under the Apache V2, see LICENCE file for details.
+from __future__ import annotations
 
 import os
 import textwrap
@@ -488,7 +489,7 @@ def user_requested(series_arg, supported_series, force):
     return series
 
 
-def series_selector(series_arg='', charm_url=None, model_config=None, supported_series=[], force=False):
+def series_selector(series_arg: str|None = "", charm_url=None, model_config=None, supported_series=[], force=False):
     """
     series_selector corresponds to the CharmSeries() in
     https://github.com/juju/juju/blob/develop/core/charm/series_selector.go