This paper focuses on the density of comment statements in a source code, and statistically analyzes an impact of the comment statement density (CSD) on the source code change rate (SCR) through a corrective maintenance. More thorough writing of comments encourages the developers to review their source code more carefully, then that leads to quality improvements of those code. An empirical study is performed with 1,820 version-upgrade cases in an open-source software, Eclipse. The empirical results show that SCR tends to increase when CSD is less than 59.5%.