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fastapi - 💡(How to fix) Fix FastAPI + Starlette 1.0.0: Jinja2 TemplateResponse raises 'unhashable type: dict' [1 participants]

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fastapi/fastapi#15197•Fetched 2026-04-08 01:16:19
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After upgrading to Starlette 1.0.0, FastAPI applications using Jinja2 templates fail with:

TypeError: cannot use 'tuple' as a dict key (unhashable type: 'dict')

at jinja2/utils.py, line 515.

Error Message

TypeError: cannot use 'tuple' as a dict key (unhashable type: 'dict')

Root Cause

After upgrading to Starlette 1.0.0, FastAPI applications using Jinja2 templates fail with:

TypeError: cannot use 'tuple' as a dict key (unhashable type: 'dict')

at jinja2/utils.py, line 515.

Fix Action

Workaround

Pin starlette<1.0.0 in requirements.txt.

Code Example

TypeError: cannot use 'tuple' as a dict key (unhashable type: 'dict')
RAW_BUFFERClick to expand / collapse

Description

After upgrading to Starlette 1.0.0, FastAPI applications using Jinja2 templates fail with:

TypeError: cannot use 'tuple' as a dict key (unhashable type: 'dict')

at jinja2/utils.py, line 515.

Environment

  • FastAPI 0.135.1
  • Starlette 1.0.0
  • Jinja2 3.1.6
  • Tested on Python 3.12 and 3.14 (issue reproduced on both)

Steps to reproduce

  1. Install fastapi==0.135.1 with starlette==1.0.0
  2. Create a route that returns a Jinja2Templates.TemplateResponse
  3. Any template render raises the error above

Workaround

Pin starlette<1.0.0 in requirements.txt.

Notes

This appears to be related to breaking changes in Starlette 1.0.0's TemplateResponse signature. FastAPI may need to update how it passes context to Jinja2 templates for Starlette 1.0.0 compatibility.

Detected in production during a routine deployment where pip resolved Starlette 1.0.0 instead of 0.52.x.

extent analysis

Fix Plan

To fix the compatibility issue between FastAPI, Starlette

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fastapi - 💡(How to fix) Fix FastAPI + Starlette 1.0.0: Jinja2 TemplateResponse raises 'unhashable type: dict' [1 participants]