diff --git a/app/core/src/main/java/com/fsck/k9/controller/MessageReference.java b/app/core/src/main/java/com/fsck/k9/controller/MessageReference.kt
similarity index 100%
rename from app/core/src/main/java/com/fsck/k9/controller/MessageReference.java
rename to app/core/src/main/java/com/fsck/k9/controller/MessageReference.kt