diff --git a/src/blob/mod.rs b/src/blob/mod.rs
index cd9ad31..dee1f73 100644
--- a/src/blob/mod.rs
+++ b/src/blob/mod.rs
@@ -223,7 +223,7 @@ impl Connection {
         row_id: i64,
         read_only: bool,
     ) -> Result<Blob<'a>> {
-        let mut c = self.db.borrow_mut();
+        let c = self.db.borrow_mut();
         let mut blob = ptr::null_mut();
         let db = db.as_cstring()?;
         let table = super::str_to_cstring(table)?;
diff --git a/src/busy.rs b/src/busy.rs
index e51fb08..b394d01 100644
--- a/src/busy.rs
+++ b/src/busy.rs
@@ -64,7 +64,7 @@ impl Connection {
                 0
             }
         }
-        let mut c = self.db.borrow_mut();
+        let c = self.db.borrow_mut();
         let r = match callback {
             Some(f) => unsafe {
                 ffi::sqlite3_busy_handler(c.db(), Some(busy_handler_callback), f as *mut c_void)
diff --git a/src/inner_connection.rs b/src/inner_connection.rs
index 11dc524..1bd641c 100644
--- a/src/inner_connection.rs
+++ b/src/inner_connection.rs
@@ -136,7 +136,7 @@ impl InnerConnection {
     }
 
     #[inline]
-    pub fn decode_result(&mut self, code: c_int) -> Result<()> {
+    pub fn decode_result(&self, code: c_int) -> Result<()> {
         unsafe { InnerConnection::decode_result_raw(self.db(), code) }
     }
 
@@ -278,7 +278,7 @@ impl InnerConnection {
     }
 
     #[inline]
-    pub fn changes(&mut self) -> usize {
+    pub fn changes(&self) -> usize {
         unsafe { ffi::sqlite3_changes(self.db()) as usize }
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index d16ffa8..71a4759 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -832,7 +832,7 @@ impl Connection {
 
     #[inline]
     fn decode_result(&self, code: c_int) -> Result<()> {
-        self.db.borrow_mut().decode_result(code)
+        self.db.borrow().decode_result(code)
     }
 
     /// Return the number of rows modified, inserted or deleted by the most
@@ -840,7 +840,7 @@ impl Connection {
     /// connection.
     #[inline]
     fn changes(&self) -> usize {
-        self.db.borrow_mut().changes()
+        self.db.borrow().changes()
     }
 
     /// Test for auto-commit mode.