Variable cannot be parametrized #20634
Description
Bug summary
The documentation of prefect.variables.Variable:aget says:
@flow
async def my_flow():
var = await Variable[str].aget("my_var")
But when i parameterize it, it gives the following error:
Encountered exception during execution: TypeError("<class 'prefect.variables.Variable'> cannot be parametrized because it does not inherit from typing.Generic")
Traceback (most recent call last):
File "/usr/local/lib/python3.12/site-packages/prefect/flow_engine.py", line 1371, in run_context
yield self
File "/usr/local/lib/python3.12/site-packages/prefect/flow_engine.py", line 1433, in run_flow_async
await engine.call_flow_fn()
File "/usr/local/lib/python3.12/site-packages/prefect/flow_engine.py", line 1385, in call_flow_fn
result = await call_with_parameters(self.flow.fn, self.parameters)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/prefect/prefect-workflows-main/prefect_wa/flows/monocle/monocle_export.py", line 138, in monocle_export
projects_variable = await Variable[str].aget("monocle-snapshot-projects")
~~~~~~~~^^^^^
File "/usr/local/lib/python3.12/site-packages/pydantic/main.py", line 898, in __class_getitem__
raise TypeError(f'{cls} cannot be parametrized because it does not inherit from typing.Generic')
TypeError: <class 'prefect.variables.Variable'> cannot be parametrized because it does not inherit from typing.Generic
Version info
Version: 3.6.16
API version: 0.8.4
Python version: 3.13.3
Git commit: e7d587cd
Built: Thu, Feb 05, 2026 07:37 PM
OS/Arch: win32/AMD64
Profile: prefect-wa-prod
Server type: server
Pydantic version: 2.12.3
Server:
Database: sqlite
SQLite version: 3.47.1
Integrations:
prefect-aws: 0.5.13
prefect-docker: 0.6.6
prefect-gitlab: 0.3.2
prefect-kubernetes: 0.7.0
prefect-redis: 0.2.6
prefect-shell: 0.3.1
Additional context
No response