diff --git a/src/core/musichoard/musichoard.rs b/src/core/musichoard/musichoard.rs
index 06720a7..266502a 100644
--- a/src/core/musichoard/musichoard.rs
+++ b/src/core/musichoard/musichoard.rs
@@ -72,7 +72,7 @@ impl<LIB, DB> MusicHoard<LIB, DB> {
         }
     }
 
-    fn merge_collections(&mut self) -> Collection {
+    fn merge_collections(&self) -> Collection {
         let mut primary = self.library_cache.clone();
         for secondary_artist in self.database_cache.iter().cloned() {
             if let Some(ref mut primary_artist) = primary.get_mut(&secondary_artist.id) {