diff --git a/androscalpel/src/apk.rs b/androscalpel/src/apk.rs
index 11f55d7..06c4c1a 100644
--- a/androscalpel/src/apk.rs
+++ b/androscalpel/src/apk.rs
@@ -3076,8 +3076,7 @@ impl Apk {
     pub fn list_classes(&self) -> HashSet<IdType> {
         self.dex_files
             .values()
-            .map(|dex| dex.classes.keys())
-            .flatten()
+            .flat_map(|dex| dex.classes.keys())
             .cloned()
             .collect()
     }