Background: Conditional compilation is often used to implement variability in configurable systems. This technique relies on #ifdefs to delimit feature code. Previous studies have shown that #ifdefs may hinder code comprehensibility. However, they did not explicitly took feature dependencies into account. Feature dependency occurs when different features refer to the same program element, such as a variable. Comprehensibility may be even more affected in the presence of feature dependency, as the developer must reason about different scenarios affecting the same variable. Aim: Our goal is to understand how feature dependency affects the comprehensibility of the configurable system source code. Method: We carried out an experiment in which 30 developers debugged programs with different types of feature dependency. We recorded the time each of them had spent to find a bug. Also, we used an eye-tracking device to record developers’ gaze movements while they debugged programs. Results: Debugging programs with global and interprocedural dependency required more time and higher visual effort. Conclusion: Our study showed that #ifdefs affect comprehensibility in different degrees depending on the type of feature dependency. Therefore, when possible, developers should take more care when dealing with code with global and interprocedural dependencies.