Antoine Chkaiban commented on PUT Asset API error

I tried the exact same second example (http://docs.shopify.com/api/asset) but I still get a "not found" error.
Would anyone have a clue about what I'm doing wrong?

Thanks,

Antoine

endpoint:
https://woopra-test.myshopify.com/admin/themes/5769313/assets.json

headers:
X-Shopify-Access-Token: *********************************

payload:
{"asset":{"source_key":"layout/theme.liquid","key":"layout/alternate.liquid"}}

response:
{"errors":"Not Found"}