diff --git a/milli/src/heed_codec/facet/field_id_codec.rs b/milli/src/heed_codec/facet/field_id_codec.rs
deleted file mode 100644
index 871b05a09..000000000
--- a/milli/src/heed_codec/facet/field_id_codec.rs
+++ /dev/null
@@ -1,28 +0,0 @@
-use std::borrow::Cow;
-use std::convert::TryInto;
-
-use heed::zerocopy::AsBytes;
-
-use crate::{FieldId, BEU16};
-
-pub struct FieldIdCodec;
-
-impl<'a> heed::BytesDecode<'a> for FieldIdCodec {
-    type DItem = FieldId;
-
-    fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
-        let bytes: [u8; 2] = bytes[..2].try_into().ok()?;
-        let field_id = BEU16::from(bytes).get();
-        Some(field_id)
-    }
-}
-
-impl<'a> heed::BytesEncode<'a> for FieldIdCodec {
-    type EItem = FieldId;
-
-    fn bytes_encode(field_id: &Self::EItem) -> Option<Cow<[u8]>> {
-        let field_id = BEU16::new(*field_id);
-        let bytes = field_id.as_bytes();
-        Some(Cow::Owned(bytes.to_vec()))
-    }
-}
diff --git a/milli/src/heed_codec/facet/mod.rs b/milli/src/heed_codec/facet/mod.rs
index 384991fd7..51812d97a 100644
--- a/milli/src/heed_codec/facet/mod.rs
+++ b/milli/src/heed_codec/facet/mod.rs
@@ -5,7 +5,9 @@ mod facet_string_level_zero_value_codec;
 mod facet_string_zero_bounds_value_codec;
 mod field_doc_id_facet_f64_codec;
 mod field_doc_id_facet_string_codec;
-mod field_id_codec;
+
+use crate::BEU16;
+use heed::types::OwnedType;
 
 pub use self::facet_level_value_f64_codec::FacetLevelValueF64Codec;
 pub use self::facet_level_value_u32_codec::FacetLevelValueU32Codec;
@@ -16,7 +18,8 @@ pub use self::facet_string_level_zero_value_codec::{
 pub use self::facet_string_zero_bounds_value_codec::FacetStringZeroBoundsValueCodec;
 pub use self::field_doc_id_facet_f64_codec::FieldDocIdFacetF64Codec;
 pub use self::field_doc_id_facet_string_codec::FieldDocIdFacetStringCodec;
-pub use self::field_id_codec::FieldIdCodec;
+
+pub type FieldIdCodec = OwnedType<BEU16>;
 
 /// Tries to split a slice in half at the given middle point,
 /// `None` if the slice is too short.
diff --git a/milli/src/index.rs b/milli/src/index.rs
index b0897271e..aec7aa396 100644
--- a/milli/src/index.rs
+++ b/milli/src/index.rs
@@ -21,7 +21,7 @@ use crate::{
     default_criteria, BEU32StrCodec, BoRoaringBitmapCodec, CboRoaringBitmapCodec, Criterion,
     DocumentId, ExternalDocumentsIds, FacetDistribution, FieldDistribution, FieldId,
     FieldIdWordCountCodec, GeoPoint, ObkvCodec, Result, RoaringBitmapCodec, RoaringBitmapLenCodec,
-    Search, StrBEU32Codec, StrStrU8Codec, BEU32,
+    Search, StrBEU32Codec, StrStrU8Codec, BEU16, BEU32,
 };
 
 pub const DEFAULT_MIN_WORD_LEN_ONE_TYPO: u8 = 5;
@@ -819,7 +819,7 @@ impl Index {
         rtxn: &RoTxn,
         field_id: FieldId,
     ) -> heed::Result<RoaringBitmap> {
-        match self.facet_id_exists_docids.get(rtxn, &field_id)? {
+        match self.facet_id_exists_docids.get(rtxn, &BEU16::new(field_id))? {
             Some(docids) => Ok(docids),
             None => Ok(RoaringBitmap::new()),
         }