Composer error

[sgatu]

I'm trying to install propelServiceProvider for Silex as the documentation shows("propel/propel-service-provider": "2.x") but I get the next error.

Problem 1
- The requested package propel/propel-service-provider 2.x is satisfiable by propel/propel-service-provider[2.x-dev] but these conflict with your requirements or minimum-stability.

There is no stable version of the library? I tried adding @dev at the end, but I think it got worse.

Problem 1
- Installation request for propel/propel-service-provider 2.x@dev -> satisfiable by propel/propel-service-provider[2.x-dev].
- propel/propel-service-provider 2.x-dev requires propel/propel ~2.0@dev -> satisfiable by propel/propel[2.0.0-alpha1, 2.0.0-alpha2, 2.0.0-alpha3, 2.0.0-alpha4, 2.0.0-alpha5, 2.0.x-dev] but these conflict with your requirements or minimum-stability.

[marcj]

you need to set minimum-stability to dev.