Various studies already exist about the lifecycle of software programs written in languages like Java, C and C++, but this is an under-reported area for the pure, functional programming language Haskell. This report explores steps in the development of Haskell programs, and particularly, of their bugs. By gaining more knowledge about a bug’s development and its different stages, possible patterns or trends can be found. Using these insights, developers could get a better understanding of the development process, and optimise it. The main question of the research is formulated as ‘What are the different stages of bugs in Haskell programs?’. We consider three different stages: bug introduction, bug detection and bug fixing. To gain more knowledge about these stages, different open-source Haskell repositories, and their bugs were analysed. We found the median time between the bug introduction and detection is 381 days. The median time between the bug detection and fixing turned out to be 3 days. Most bugs were detected and fixed at similar rates regardless of their complexity, except for bugs that were detected by the same developer who introduced the bug. In this case, the time it takes to detect the bug is 30% of the global median. These results motivate developers to check their code more extensively, as they detect bugs quicker than other developers would. It also motivates developers to work with shared code ownership, as having more developers familiar with the code should reduce bug-detection time. Moreover, this study shows that single-statement bugs, which needed a simple fix, occur 2.5 times more often in code when no test is written, which argues for developers to write more test code. Lastly, we recommend repository owners to be more strict with developers working structured and precisely so that they follow Git’s and the repository’s standards and write test code.