diff --git a/heed-traits/src/lib.rs b/heed-traits/src/lib.rs
index 50efad2c..adf0c14a 100644
--- a/heed-traits/src/lib.rs
+++ b/heed-traits/src/lib.rs
@@ -55,7 +55,7 @@ pub trait BytesEncode<'a> {
     /// The default implementation forwards to [`bytes_encode`][BytesEncode::bytes_encode].
     fn bytes_encode_into_writer<W: io::Write>(
         item: &'a Self::EItem,
-        writer: &mut W,
+        mut writer: W,
     ) -> Result<(), BoxedError> {
         let bytes = Self::bytes_encode(item)?;
 
diff --git a/heed-types/src/serde_bincode.rs b/heed-types/src/serde_bincode.rs
index dfb555d9..d65ce05f 100644
--- a/heed-types/src/serde_bincode.rs
+++ b/heed-types/src/serde_bincode.rs
@@ -26,7 +26,7 @@ where
 
     fn bytes_encode_into_writer<W: std::io::Write>(
         item: &'a Self::EItem,
-        writer: &mut W,
+        writer: W,
     ) -> Result<(), BoxedError> {
         bincode::serialize_into(writer, item)?;
         Ok(())
diff --git a/heed-types/src/serde_json.rs b/heed-types/src/serde_json.rs
index b093b147..80624ff2 100644
--- a/heed-types/src/serde_json.rs
+++ b/heed-types/src/serde_json.rs
@@ -26,7 +26,7 @@ where
 
     fn bytes_encode_into_writer<W: std::io::Write>(
         item: &'a Self::EItem,
-        writer: &mut W,
+        writer: W,
     ) -> Result<(), BoxedError> {
         serde_json::to_writer(writer, item)?;
         Ok(())
diff --git a/heed-types/src/serde_rmp.rs b/heed-types/src/serde_rmp.rs
index f866519b..00127131 100644
--- a/heed-types/src/serde_rmp.rs
+++ b/heed-types/src/serde_rmp.rs
@@ -26,9 +26,9 @@ where
 
     fn bytes_encode_into_writer<W: std::io::Write>(
         item: &'a Self::EItem,
-        writer: &mut W,
+        mut writer: W,
     ) -> Result<(), BoxedError> {
-        rmp_serde::encode::write(writer, item)?;
+        rmp_serde::encode::write(&mut writer, item)?;
         Ok(())
     }
 }