diff --git a/llm/cli.py b/llm/cli.py
index b3c144bf..1a7519cf 100644
--- a/llm/cli.py
+++ b/llm/cli.py
@@ -521,7 +521,7 @@ def chat(
                 raise click.ClickException(str(ex))
         if prompt.strip() in ("exit", "quit"):
             break
-        response = conversation.prompt(prompt, system, **validated_options)
+        response = conversation.prompt(prompt, system=system, **validated_options)
         # System prompt only sent for the first message:
         system = None
         for chunk in response:
diff --git a/llm/models.py b/llm/models.py
index 06440eed..6364c27e 100644
--- a/llm/models.py
+++ b/llm/models.py
@@ -85,11 +85,18 @@ class Prompt:
     options: "Options" = field(default_factory=dict)
 
     def __init__(
-        self, prompt, model, attachments, system=None, prompt_json=None, options=None
+        self,
+        prompt,
+        model,
+        *,
+        attachments=None,
+        system=None,
+        prompt_json=None,
+        options=None
     ):
         self.prompt = prompt
         self.model = model
-        self.attachments = list(attachments)
+        self.attachments = list(attachments or [])
         self.system = system
         self.prompt_json = prompt_json
         self.options = options or {}
@@ -105,7 +112,8 @@ class Conversation:
     def prompt(
         self,
         prompt: Optional[str],
-        *attachments: Attachment,
+        *,
+        attachments: Attachment = None,
         system: Optional[str] = None,
         stream: bool = True,
         **options
@@ -386,7 +394,8 @@ def execute(
     def prompt(
         self,
         prompt: str,
-        *attachments: Attachment,
+        *,
+        attachments: Attachment = None,
         system: Optional[str] = None,
         stream: bool = True,
         **options
@@ -396,7 +405,7 @@ def prompt(
             raise ValueError(
                 "This model does not support attachments, but some were provided"
             )
-        for attachment in attachments:
+        for attachment in attachments or []:
             attachment_type = attachment.resolve_type()
             if attachment_type not in self.attachment_types:
                 raise ValueError(
diff --git a/tests/test_chat.py b/tests/test_chat.py
index cf7ddeff..01b2a0c0 100644
--- a/tests/test_chat.py
+++ b/tests/test_chat.py
@@ -23,7 +23,10 @@ def test_chat_basic(mock_model, logs_db):
     mock_model.enqueue(["one world"])
     mock_model.enqueue(["one again"])
     result = runner.invoke(
-        llm.cli.cli, ["chat", "-m", "mock"], input="Hi\nHi two\nquit\n"
+        llm.cli.cli,
+        ["chat", "-m", "mock"],
+        input="Hi\nHi two\nquit\n",
+        catch_exceptions=False,
     )
     assert result.exit_code == 0
     assert result.output == (