Programming is an essential skill that many computing students are expected to master. However, programming can be difficult to learn. Successfully interpreting compiler error messages (CEMs) is crucial for correcting errors and progressing toward success in programming. Yet these messages are often difficult to understand and pose a barrier to progress for many novices, with struggling students often exhibiting high frequencies of errors, particularly repeated errors. This paper presents a control/intervention study on the effectiveness of enhancing Java CEMs. Results show that the intervention group experienced reductions in the number of overall errors, errors per student, and several repeated error metrics. These results are important as the effectiveness of CEM enhancement has been recently debated. Further, generalizing these results should be possible at least in part, as the control group is shown to be comparable to those in several studies using Java and other languages.