Weak equivalence principle (the bodies are gravitating equally per inertial mass irrespective of the chemical composition) was confirmed for barionic matter with very high accuracy. However, a priory it is not clear, how to check weak equivalence principle for the mixture of barionic and non-barionic matter (light is inside the ordinary matter). For example, how fast would the sphere full of photons fall in the Earth gravity field? The experiment is not possible on Earth. However, such verification is possible for stars using the observational data on binary stars. In this article the analysis of the mass-luminosity was made for similar stars forming binary versus different stars forming binary and the slopes were found the same with accuracy of 6%. That would be the accuracy of confirmation of the equivalence principle for non-barionic matter (actually a mixture of barionic and non-barionic matter with around 0.14% of non-barionic matter ratio). While some violations of weak equivalence principle are still possible (the idea of strong gravitation of slow light) the scale of such violations is clearly well below the level expected for explanation of dark matter.