diff --git a/chatmastermind/chat.py b/chatmastermind/chat.py
index 5f15a64..6ea28ff 100644
--- a/chatmastermind/chat.py
+++ b/chatmastermind/chat.py
@@ -52,7 +52,7 @@ def read_dir(dir_path: Path,
     Parameters:
     * 'dir_path': source directory
     * 'glob': if specified, files will be filtered using 'path.glob()',
-      otherwise it uses '*{msg_suffix}'.
+      otherwise it reads all files with the default message suffix
     * 'mfilter': use with 'Message.from_file()' to filter messages
       when reading them.
     """
@@ -295,7 +295,7 @@ class ChatDB(Chat):
     # a MessageFilter that all messages must match (if given)
     mfilter: Optional[MessageFilter] = None
     # the glob pattern for all messages
-    glob: Optional[str] = None
+    glob: str = f'*{msg_suffix}'
     # message format (for writing)
     mformat: MessageFormat = Message.default_format
 
@@ -311,7 +311,7 @@ class ChatDB(Chat):
     def from_dir(cls: Type[ChatDBInst],
                  cache_path: Path,
                  db_path: Path,
-                 glob: Optional[str] = None,
+                 glob: str = f'*{msg_suffix}',
                  mfilter: Optional[MessageFilter] = None,
                  loc: msg_location = msg_location.DB) -> ChatDBInst:
         """
@@ -320,8 +320,7 @@ class ChatDB(Chat):
         Parameters:
         * 'cache_path': path to the directory for temporary messages
         * 'db_path': path to the directory for persistent messages
-        * 'glob': if specified, files will be filtered using 'path.glob()',
-          otherwise it uses 'path.iterdir()'.
+        * 'glob': if specified, files will be filtered using 'path.glob()'
         * 'mfilter': use with 'Message.from_file()' to filter messages
           when reading them.
         """
@@ -400,7 +399,7 @@ class ChatDB(Chat):
     def msg_gather(self,
                    loc: msg_location,
                    require_file_path: bool = False,
-                   glob: Optional[str] = None,
+                   glob: str = f'*{msg_suffix}',
                    mfilter: Optional[MessageFilter] = None) -> list[Message]:
         """
         Gather and return messages from the given locations:
@@ -520,7 +519,7 @@ class ChatDB(Chat):
         else:
             return len(self.msg_find([message], loc=msg_location.DB)) > 0
 
-    def cache_read(self, glob: Optional[str] = None, mfilter: Optional[MessageFilter] = None) -> None:
+    def cache_read(self, glob: str = f'*{msg_suffix}', mfilter: Optional[MessageFilter] = None) -> None:
         """
         Read messages from the cache directory. New ones are added to the internal list,
         existing ones are replaced. A message is determined as 'existing' if a message
@@ -563,7 +562,7 @@ class ChatDB(Chat):
         self.messages += messages
         self.msg_sort()
 
-    def cache_clear(self, glob: Optional[str] = None) -> None:
+    def cache_clear(self, glob: str = f'*{msg_suffix}') -> None:
         """
         Delete all message files from the cache dir and remove them from the internal list.
         """
@@ -587,7 +586,7 @@ class ChatDB(Chat):
         # (re)add it to the internal list
         self.msg_add([message])
 
-    def db_read(self, glob: Optional[str] = None, mfilter: Optional[MessageFilter] = None) -> None:
+    def db_read(self, glob: str = f'*{msg_suffix}', mfilter: Optional[MessageFilter] = None) -> None:
         """
         Read messages from the DB directory. New ones are added to the internal list,
         existing ones are replaced. A message is determined as 'existing' if a message