diff --git a/src/main.rs b/src/main.rs
index a1f856d..6c0a430 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -542,7 +542,7 @@ fn mode_diff(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec<S
                 let item_path_a = item_path_a.clone();
                 let compression_type_a = compression_type_a.clone();
                 std::thread::spawn(move || {
-                    let stdout_a = BufWriter::new(stdout_a_raw);
+                    let mut stdout_a = BufWriter::new(stdout_a_raw);
                     let compression_engine_a = compression::get_engine(compression_type_a).expect("Unable to get compression engine");
                     compression_engine_a.copy(item_path_a, &mut stdout_a).unwrap()
                 })
@@ -554,7 +554,7 @@ fn mode_diff(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec<S
                 let item_path_b = item_path_b.clone();
                 let compression_type_b = compression_type_b.clone();
                 std::thread::spawn(move || {
-                    let stdout_b = BufWriter::new(stdout_b_raw);
+                    let mut stdout_b = BufWriter::new(stdout_b_raw);
                     let compression_engine_b = compression::get_engine(compression_type_b).expect("Unable to get compression engine");
                     compression_engine_b.copy(item_path_b, &mut stdout_b).unwrap()
                 })