diff --git a/docs/registry.md b/docs/registry.md
index c8f9def..cb3666b 100644
--- a/docs/registry.md
+++ b/docs/registry.md
@@ -1,5 +1,8 @@
-## Template registry
+## Template registry (BETA)
 
-::: banks.registry.TemplateRegistry
+Template registry is a storage API for versioned prompts. It allows you to store and retrieve templates from local storage.
+Currently, it supports storing templates in a JSON file, but it can be extended to support other storage backends.
 
-::: banks.registry.PromptTemplate
+### Usage
+
+Coming soon.
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
index 16b6855..8ec4b8c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ name = "banks"
 dynamic = ["version"]
 description = 'A prompt programming language'
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = "MIT"
 keywords = []
 authors = [
diff --git a/src/banks/registries/file.py b/src/banks/registries/file.py
index f2525e6..7fe7f07 100644
--- a/src/banks/registries/file.py
+++ b/src/banks/registries/file.py
@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: MIT
 from pathlib import Path
 
-from banks.registry import PromptTemplate, PromptTemplateIndex, TemplateNotFoundError
+from banks.registry import PromptTemplate, PromptTemplateIndex, TemplateNotFoundError, InvalidTemplateError
 
 
 class FileTemplateRegistry:
@@ -18,6 +18,8 @@ def __init__(self, user_data_path: Path) -> None:
 
     @staticmethod
     def _make_id(name: str, version: str | None):
+        if ":" in name:
+            raise InvalidTemplateError("Template name cannot contain ':'")
         if version:
             return f"{name}:{version}"
         return name
diff --git a/src/banks/registry.py b/src/banks/registry.py
index 976111e..19b5c0e 100644
--- a/src/banks/registry.py
+++ b/src/banks/registry.py
@@ -9,6 +9,9 @@
 class TemplateNotFoundError(Exception): ...
 
 
+class InvalidTemplateError(Exception): ...
+
+
 class PromptTemplate(BaseModel):
     id: str
     name: str
diff --git a/tests/test_file_registry.py b/tests/test_file_registry.py
index 5647db4..98617e2 100644
--- a/tests/test_file_registry.py
+++ b/tests/test_file_registry.py
@@ -1,7 +1,7 @@
 import pytest
 
 from banks.registries.file import FileTemplateRegistry
-from banks.registry import PromptTemplate, PromptTemplateIndex, TemplateNotFoundError
+from banks.registry import PromptTemplate, PromptTemplateIndex, TemplateNotFoundError, InvalidTemplateError
 
 
 @pytest.fixture
@@ -31,9 +31,11 @@ def test_init_from_existing_index(populated_index_dir):
     r.get("name", "version")
 
 
-def test__make_id():
+def test_make_id():
     assert FileTemplateRegistry._make_id("name", "version") == "name:version"
     assert FileTemplateRegistry._make_id("name", None) == "name"
+    with pytest.raises(InvalidTemplateError, match="Template name cannot contain ':'"):
+        _ = FileTemplateRegistry._make_id("name:version", None)
 
 
 def test_get(populated_index_dir):