Software design patterns are used to improve the software quality. There are distinct kinds of software, as well as design patterns. One of them is patterns for enterprise application architecture. Although enterprise design patterns are said to be able to improve the software quality, there is a lack of literature that discusses the evidence of the impact. This preliminary study proposes a method to assess the impact of enterprise software design pattern on maintainability. We use the Academic Information System (AIS) of Institut Teknologi Sepuluh Nopember (ITS) as a case study. It is enterprise software which is frequently maintained and need to be evolved. The software maintainability is measured by using CK metrics. Then we calculate the relative change and evaluate it based on viewpoints of the metrics. Transaction Script pattern is selected to verify the method. As a result, it decreases the maintainability instead of improving it. The result of this preliminary study shows that design patterns did not improve the software maintainability. Based on the previous researches, it depends on several factors which may be studied in the future work. Thus, we need to propose a method to select the appropriate patterns or whether we use design patterns or not.