diff --git a/os/src/mm/memory_set.rs b/os/src/mm/memory_set.rs
index 7cdd394a9..10e164a7e 100644
--- a/os/src/mm/memory_set.rs
+++ b/os/src/mm/memory_set.rs
@@ -316,7 +316,7 @@ impl MapArea {
     }
     /// data: start-aligned but maybe with shorter length
     /// assume that all frames were cleared before
-    pub fn copy_data(&mut self, page_table: &mut PageTable, data: &[u8]) {
+    pub fn copy_data(&mut self, page_table: &PageTable, data: &[u8]) {
         assert_eq!(self.map_type, MapType::Framed);
         let mut start: usize = 0;
         let mut current_vpn = self.vpn_range.get_start();