diff --git a/lektor_groupby/plugin.py b/lektor_groupby/plugin.py
index c9fc1c1..9f92f9b 100644
--- a/lektor_groupby/plugin.py
+++ b/lektor_groupby/plugin.py
@@ -42,8 +42,8 @@ class GroupByPlugin(Plugin):
             def _fn(args: GroupByCallbackArgs) -> Iterator[str]:
                 val = args.field
                 if isinstance(val, str):
-                    val = val.split(split) if split else [val]  # make list
-                if isinstance(val, list):
+                    val = map(str.strip, val.split(split)) if split else [val]
+                if isinstance(val, (list, map)):
                     yield from val
 
     def on_before_build_all(self, builder: Builder, **extra: object) -> None:
diff --git a/lektor_groupby/vobj.py b/lektor_groupby/vobj.py
index 02f2c50..17f097f 100644
--- a/lektor_groupby/vobj.py
+++ b/lektor_groupby/vobj.py
@@ -121,7 +121,7 @@ class GroupBySource(VirtualSourceObject):
 
     def __lt__(self, other: 'GroupBySource') -> bool:
         # Used for |sort filter ("group" is the provided original string)
-        return self.group < other.group
+        return self.group.lower() < other.group.lower()
 
     def __eq__(self, other: object) -> bool:
         # Used for |unique filter
diff --git a/lektor_groupby/watcher.py b/lektor_groupby/watcher.py
index a120ae2..230b929 100644
--- a/lektor_groupby/watcher.py
+++ b/lektor_groupby/watcher.py
@@ -150,7 +150,7 @@ class Watcher:
                 while True:
                     if not isinstance(obj, (str, tuple)):
                         raise TypeError(f'Unsupported groupby yield: {obj}')
-                    slug = self._persist(record, obj)
+                    slug = self._persist(record, key, obj)
                     # return slugified group key and continue iteration
                     if isinstance(_gen, Generator) and not _gen.gi_yieldfrom:
                         obj = _gen.send(slug)
@@ -159,7 +159,12 @@ class Watcher:
             except StopIteration:
                 del _gen
 
-    def _persist(self, record: Record, obj: Union[str, tuple]) -> str:
+    def _persist(
+        self,
+        record: Record,
+        key: FieldKeyPath,
+        obj: Union[str, tuple]
+    ) -> str:
         group = obj if isinstance(obj, str) else obj[0]
         slug = self.config.slugify(group)
         # init group-key
@@ -174,6 +179,8 @@ class Watcher:
         # (optional) append extra
         if isinstance(obj, tuple):
             self._state[slug][record].append(obj[1])
+        else:
+            self._state[slug][record].append(key.flowKey or key.fieldKey)
         return slug
 
     def iter_sources(self, root: Record) -> Iterator[GroupBySource]:
diff --git a/setup.py b/setup.py
index 0eb7c54..389792d 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@ with open('README.md') as fp:
 
 setup(
     name='lektor-groupby',
-    py_modules=['lektor_groupby'],
+    packages=['lektor_groupby'],
     entry_points={
         'lektor.plugins': [
             'groupby = lektor_groupby:GroupByPlugin',