Visible demographic characteristics are seen as elements of bias in offline work environments. In this study, we investigate the influence of the geographical location on the evaluation of pull requests in GitHub - the most popular online collaborative code development environment. We use a mixed-methods approach and present analyses of 70,000+ pull requests and 2,500+ survey responses. Quantitative analysis of GitHub projects' data suggests that the geographical location significantly explains the pull request acceptance decisions. These observations are in agreement with the perceptions of submitters based on their experiences with bias. Integrators feel that it is easy to work with contributors from the same geographical location and that they encourage contributors from the same geographical location. However, integrators do not feel that contributors from some countries are better at writing pull requests compared to others.