diff --git a/favro_sync/favro_fuse.py b/favro_sync/favro_fuse.py
index c257a47..e1e4e65 100644
--- a/favro_sync/favro_fuse.py
+++ b/favro_sync/favro_fuse.py
@@ -26,7 +26,7 @@ CARD_FILENAME_REGEX = r'^PAR\-(\d+)\.md$'
 ################################################################################
 # Formatting
 
-def to_custom_field_value(custom_field: CustomField, field_def: CustomFieldInfo) -> str:
+def to_custom_field_value(custom_field: CustomField, field_def: CustomFieldInfo) -> str | None:
     value: CustomFieldItemId | list[CustomFieldItemId] = custom_field.value
     if field_def.type in {'Single select','Multiple select'}:
         items = [field_def.get_field_item(item_id) for item_id in value]
@@ -34,17 +34,19 @@ def to_custom_field_value(custom_field: CustomField, field_def: CustomFieldInfo)
         return items[0].name
     if field_def.type in {'Color'}:
         return custom_field.color
-    assert False, 'Unknown type: ' + field_def.type
+    return None
 
 def to_custom_fields(card: Card, favro_client: FavroClient) -> dict[str,str]:
     custom_fields = {}
     for field_assignment in card.custom_fields:
         field_def = favro_client.get_custom_field(field_assignment.custom_field_id)
-        custom_fields[field_def.name] = to_custom_field_value(field_assignment, field_def)
-        del field_assignment
+        str_value = to_custom_field_value(field_assignment, field_def)
+        if str_value is not None:
+            custom_fields[field_def.name] = str_value
+        del field_assignment, str_value
     return custom_fields
 
-def to_card_contents(card: Card, favro_client: FavroClient) -> str:
+def to_card_contents(card: Card, favro_client: FavroClient) -> CardContents:
     tags = [favro_client.get_tag(tag_id).name for tag_id in card.tags]
     assignments = [
         favro_client.get_user(assignment.user).name for assignment in card.assignments
@@ -101,7 +103,7 @@ class FileSystemItem:
 class RootFileSystemItem(FileSystemItem):
 
     @staticmethod
-    def from_path_segment(segment: str) -> 'RootFileSystemItem':
+    def from_path_segment(_segment: str) -> 'RootFileSystemItem':
         return RootFileSystemItem()
 
     def __str__(self):
@@ -111,6 +113,9 @@ class RootFileSystemItem(FileSystemItem):
 class CollectionFileSystemItem(FileSystemItem):
     collection_name: str
 
+    def __post_init__(self):
+        assert '/' not in self.collection_name
+
     @staticmethod
     def from_path_segment(segment: str) -> 'CollectionFileSystemItem':
         return CollectionFileSystemItem(segment)
@@ -155,7 +160,6 @@ class FavroFuse(fuse.Fuse):
 
     def getattr(self, path: str) -> FavroStat | int:
         file_system_item = path_to_file_system_item(path, self.path_components)
-        print(file_system_item )
 
         st = FavroStat()
         if isinstance(file_system_item, RootFileSystemItem | CollectionFileSystemItem):
@@ -181,19 +185,18 @@ class FavroFuse(fuse.Fuse):
 
         if isinstance(file_system_item, RootFileSystemItem):
             for collection in self.favro_client.get_collections():
-                print(collection)
-                yield fuse.Direntry(str(CollectionFileSystemItem(collection.name)))
+                collection_name = collection.name.replace('/', '')
+                yield fuse.Direntry(str(CollectionFileSystemItem(collection_name)))
                 del collection
+
         elif isinstance(file_system_item, CollectionFileSystemItem):
 
             # TODO: move into own function
             for collection in self.favro_client.get_collections():
-                if collection.name == file_system_item.collection_name:
+                if collection.name.replace('/', '') == file_system_item.collection_name:
                     collection_id = collection.collection_id
                 del collection
 
-            print('Collection', collection_id)
-
             for card in self.favro_client.get_cards(collection_id=collection_id):
                 yield fuse.Direntry(str(CardFileSystemItem(card.seq_id)))
                 del card