We derive a model in which a standard international capital asset pricing model (ICAPM) for government bonds is nested within an ICAPM with impediments to invest in the local government bond markets. Excess returns or risk premiums are then driven by a country-specific or idiosyncratic stochastic factor on top of the common factor which has a time-varying idiosyncratic impact on the premiums. With this model we investigate the financial integration of government bond markets over time through two channels. First, we allow for gradual convergence from the full ICAPM with impediments to the standard model through the vanishing of the idiosyncratic factors. Second, we allow for gradual equalization of the country-specific impacts of the common factor. State space methods are used to estimate the model with weekly government bond risk premiums for Belgium, France, Italy, Germany, and the Netherlands over the period 1995-2009. Our results suggest, first, that the idiosyncratic factors were almost eliminated by 2006 in all countries but Italy but then reappeared due to the financial crisis that started in 2007. Second, the country-specific exposures to the common international risk factor have converged across countries, with no setback during the crisis.