diff --git a/meilidb-data/src/database.rs b/meilidb-data/src/database.rs
index 667baf2e0..e2fb2db6a 100644
--- a/meilidb-data/src/database.rs
+++ b/meilidb-data/src/database.rs
@@ -225,7 +225,7 @@ impl MainIndex {
     fn ranked_map(&self) -> Result<Option<RankedMap>, Error> {
         match self.0.get("ranked-map")? {
             Some(bytes) => {
-                let ranked_map = bincode::deserialize(bytes.as_ref())?;
+                let ranked_map = RankedMap::read_from_bin(bytes.as_ref())?;
                 Ok(Some(ranked_map))
             },
             None => Ok(None),
@@ -309,7 +309,7 @@ impl RawIndex {
 
         let ranked_map = {
             let map = match inner.get("ranked-map")? {
-                Some(bytes) => bincode::deserialize(bytes.as_ref())?,
+                Some(bytes) => RankedMap::read_from_bin(bytes.as_ref())?,
                 None => RankedMap::default(),
             };
 
@@ -355,8 +355,10 @@ impl RawIndex {
     }
 
     pub fn update_ranked_map(&self, ranked_map: Arc<RankedMap>) -> sled::Result<()> {
-        let data = bincode::serialize(ranked_map.as_ref()).unwrap();
-        self.inner.set("ranked-map", data).map(drop)?;
+        let mut bytes = Vec::new();
+        ranked_map.as_ref().write_to_bin(&mut bytes).unwrap();
+
+        self.inner.set("ranked-map", bytes).map(drop)?;
         self.ranked_map.store(ranked_map);
 
         Ok(())
diff --git a/meilidb-data/src/ranked_map.rs b/meilidb-data/src/ranked_map.rs
index 7b4ff3735..aea7c8b20 100644
--- a/meilidb-data/src/ranked_map.rs
+++ b/meilidb-data/src/ranked_map.rs
@@ -1,5 +1,27 @@
+use std::io::{Read, Write};
+
 use hashbrown::HashMap;
 use meilidb_core::DocumentId;
+
 use crate::{SchemaAttr, Number};
 
-pub type RankedMap = HashMap<(DocumentId, SchemaAttr), Number>;
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+pub struct RankedMap(HashMap<(DocumentId, SchemaAttr), Number>);
+
+impl RankedMap {
+    pub fn insert(&mut self, document: DocumentId, attribute: SchemaAttr, number: Number) {
+        self.0.insert((document, attribute), number);
+    }
+
+    pub fn get(&self, document: DocumentId, attribute: SchemaAttr) -> Option<Number> {
+        self.0.get(&(document, attribute)).cloned()
+    }
+
+    pub fn read_from_bin<R: Read>(reader: R) -> bincode::Result<RankedMap> {
+        bincode::deserialize_from(reader).map(RankedMap)
+    }
+
+    pub fn write_to_bin<W: Write>(&self, writer: W) -> bincode::Result<()> {
+        bincode::serialize_into(writer, &self.0)
+    }
+}
diff --git a/meilidb-data/src/serde/serializer.rs b/meilidb-data/src/serde/serializer.rs
index 1857fe134..6f4ad3608 100644
--- a/meilidb-data/src/serde/serializer.rs
+++ b/meilidb-data/src/serde/serializer.rs
@@ -285,9 +285,8 @@ where T: ser::Serialize,
         }
 
         if props.is_ranked() {
-            let key = (document_id, attr);
             let number = value.serialize(ConvertToNumber)?;
-            ranked_map.insert(key, number);
+            ranked_map.insert(document_id, attr, number);
         }
     }
 
diff --git a/meilidb/src/sort_by_attr.rs b/meilidb/src/sort_by_attr.rs
index f4c4bcc41..2cacaae13 100644
--- a/meilidb/src/sort_by_attr.rs
+++ b/meilidb/src/sort_by_attr.rs
@@ -87,8 +87,8 @@ impl<'a> SortByAttr<'a> {
 
 impl<'a> Criterion for SortByAttr<'a> {
     fn evaluate(&self, lhs: &RawDocument, rhs: &RawDocument) -> Ordering {
-        let lhs = self.ranked_map.get(&(lhs.id, self.attr));
-        let rhs = self.ranked_map.get(&(rhs.id, self.attr));
+        let lhs = self.ranked_map.get(lhs.id, self.attr);
+        let rhs = self.ranked_map.get(rhs.id, self.attr);
 
         match (lhs, rhs) {
             (Some(lhs), Some(rhs)) => {