When I tried to upgrade my phone 3GS 3.x to a 4.x firmware found on osxdaily.com, I got the famous “this device isn’t eligible for the requested build”.

My jailbroken device was on a 3.1.3 firmware with Cydia installed. After trying different 4.x firmwares, I googled this error message and found an interesting thread here.

I followed their advice and it worked:

• Install TinyUmbrella,
• Clicked on my device,
• went to Advanced tab and unchecked “Request SHSH from Cydia”,
• Started TSS Server,
• Entered Recovery,
• and finally in iTunes clicked on Restore (with option key) and selected a 4.1 firmware,
• done!