diff --git a/lib/src/working_copy.rs b/lib/src/working_copy.rs
index e7922e9d2..124173991 100644
--- a/lib/src/working_copy.rs
+++ b/lib/src/working_copy.rs
@@ -63,7 +63,7 @@ pub struct FileState {
 
 impl FileState {
     #[cfg_attr(unix, allow(dead_code))]
-    fn is_executable(&mut self) -> bool {
+    fn is_executable(&self) -> bool {
         if let FileType::Normal { executable } = &self.file_type {
             *executable
         } else {