diff --git a/milli/src/heed_codec/facet/field_doc_id_facet_codec.rs b/milli/src/heed_codec/facet/field_doc_id_facet_codec.rs
index a0bea2c42..7e281adfa 100644
--- a/milli/src/heed_codec/facet/field_doc_id_facet_codec.rs
+++ b/milli/src/heed_codec/facet/field_doc_id_facet_codec.rs
@@ -3,6 +3,7 @@ use std::marker::PhantomData;
 
 use heed::{BoxedError, BytesDecode, BytesEncode};
 
+use crate::heed_codec::SliceTooShortError;
 use crate::{try_split_array_at, DocumentId, FieldId};
 
 pub struct FieldDocIdFacetCodec<C>(PhantomData<C>);
@@ -14,10 +15,10 @@ where
     type DItem = (FieldId, DocumentId, C::DItem);
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
-        let (field_id_bytes, bytes) = try_split_array_at(bytes).unwrap();
+        let (field_id_bytes, bytes) = try_split_array_at(bytes).ok_or(SliceTooShortError)?;
         let field_id = u16::from_be_bytes(field_id_bytes);
 
-        let (document_id_bytes, bytes) = try_split_array_at(bytes).unwrap();
+        let (document_id_bytes, bytes) = try_split_array_at(bytes).ok_or(SliceTooShortError)?;
         let document_id = u32::from_be_bytes(document_id_bytes);
 
         let value = C::bytes_decode(bytes)?;
diff --git a/milli/src/heed_codec/facet/ordered_f64_codec.rs b/milli/src/heed_codec/facet/ordered_f64_codec.rs
index 64bb0b0cd..b692b2363 100644
--- a/milli/src/heed_codec/facet/ordered_f64_codec.rs
+++ b/milli/src/heed_codec/facet/ordered_f64_codec.rs
@@ -2,8 +2,10 @@ use std::borrow::Cow;
 use std::convert::TryInto;
 
 use heed::{BoxedError, BytesDecode};
+use thiserror::Error;
 
 use crate::facet::value_encoding::f64_into_bytes;
+use crate::heed_codec::SliceTooShortError;
 
 pub struct OrderedF64Codec;
 
@@ -12,7 +14,7 @@ impl<'a> BytesDecode<'a> for OrderedF64Codec {
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
         if bytes.len() < 16 {
-            Err(BoxedError::from("invalid slice length"))
+            Err(SliceTooShortError.into())
         } else {
             bytes[8..].try_into().map(f64::from_be_bytes).map_err(Into::into)
         }
@@ -26,8 +28,7 @@ impl heed::BytesEncode<'_> for OrderedF64Codec {
         let mut buffer = [0u8; 16];
 
         // write the globally ordered float
-        let bytes = f64_into_bytes(*f)
-            .ok_or_else(|| BoxedError::from("cannot generate a globally ordered float"))?;
+        let bytes = f64_into_bytes(*f).ok_or(InvalidGloballyOrderedFloatError { float: *f })?;
         buffer[..8].copy_from_slice(&bytes[..]);
         // Then the f64 value just to be able to read it back
         let bytes = f.to_be_bytes();
@@ -36,3 +37,9 @@ impl heed::BytesEncode<'_> for OrderedF64Codec {
         Ok(Cow::Owned(buffer.to_vec()))
     }
 }
+
+#[derive(Error, Debug)]
+#[error("the float {float} cannot be converted to a globally ordered representation")]
+pub struct InvalidGloballyOrderedFloatError {
+    float: f64,
+}
diff --git a/milli/src/heed_codec/field_id_word_count_codec.rs b/milli/src/heed_codec/field_id_word_count_codec.rs
index 9e7f044c5..19d8d63c6 100644
--- a/milli/src/heed_codec/field_id_word_count_codec.rs
+++ b/milli/src/heed_codec/field_id_word_count_codec.rs
@@ -2,6 +2,7 @@ use std::borrow::Cow;
 
 use heed::BoxedError;
 
+use super::SliceTooShortError;
 use crate::{try_split_array_at, FieldId};
 
 pub struct FieldIdWordCountCodec;
@@ -10,11 +11,9 @@ impl<'a> heed::BytesDecode<'a> for FieldIdWordCountCodec {
     type DItem = (FieldId, u8);
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
-        let (field_id_bytes, bytes) =
-            try_split_array_at(bytes).ok_or("invalid slice length").map_err(BoxedError::from)?;
+        let (field_id_bytes, bytes) = try_split_array_at(bytes).ok_or(SliceTooShortError)?;
         let field_id = u16::from_be_bytes(field_id_bytes);
-        let ([word_count], _nothing) =
-            try_split_array_at(bytes).ok_or("invalid slice length").map_err(BoxedError::from)?;
+        let ([word_count], _nothing) = try_split_array_at(bytes).ok_or(SliceTooShortError)?;
         Ok((field_id, word_count))
     }
 }
diff --git a/milli/src/heed_codec/mod.rs b/milli/src/heed_codec/mod.rs
index dde77a5f3..449d1955c 100644
--- a/milli/src/heed_codec/mod.rs
+++ b/milli/src/heed_codec/mod.rs
@@ -15,6 +15,7 @@ mod str_str_u8_codec;
 pub use byte_slice_ref::BytesRefCodec;
 use heed::BoxedError;
 pub use str_ref::StrRefCodec;
+use thiserror::Error;
 
 pub use self::beu16_str_codec::BEU16StrCodec;
 pub use self::beu32_str_codec::BEU32StrCodec;
@@ -34,3 +35,7 @@ pub trait BytesDecodeOwned {
 
     fn bytes_decode_owned(bytes: &[u8]) -> Result<Self::DItem, BoxedError>;
 }
+
+#[derive(Error, Debug)]
+#[error("the slice is too short")]
+pub struct SliceTooShortError;
diff --git a/milli/src/heed_codec/script_language_codec.rs b/milli/src/heed_codec/script_language_codec.rs
index 013ec62bb..ef2ad4bec 100644
--- a/milli/src/heed_codec/script_language_codec.rs
+++ b/milli/src/heed_codec/script_language_codec.rs
@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::ffi::CStr;
 use std::str;
 
 use charabia::{Language, Script};
@@ -10,17 +11,12 @@ impl<'a> heed::BytesDecode<'a> for ScriptLanguageCodec {
     type DItem = (Script, Language);
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
-        let sep = bytes
-            .iter()
-            .position(|b| *b == 0)
-            .ok_or("cannot find nul byte")
-            .map_err(BoxedError::from)?;
-        let (s_bytes, l_bytes) = bytes.split_at(sep);
-        let script = str::from_utf8(s_bytes)?;
+        let cstr = CStr::from_bytes_until_nul(bytes)?;
+        let script = cstr.to_str()?;
         let script_name = Script::from_name(script);
-        let lan = str::from_utf8(l_bytes)?;
         // skip '\0' byte between the two strings.
-        let lan_name = Language::from_name(&lan[1..]);
+        let lan = str::from_utf8(&bytes[script.len() + 1..])?;
+        let lan_name = Language::from_name(lan);
 
         Ok((script_name, lan_name))
     }
diff --git a/milli/src/heed_codec/str_beu32_codec.rs b/milli/src/heed_codec/str_beu32_codec.rs
index c654a1811..c76ea2a26 100644
--- a/milli/src/heed_codec/str_beu32_codec.rs
+++ b/milli/src/heed_codec/str_beu32_codec.rs
@@ -5,6 +5,8 @@ use std::str;
 
 use heed::BoxedError;
 
+use super::SliceTooShortError;
+
 pub struct StrBEU32Codec;
 
 impl<'a> heed::BytesDecode<'a> for StrBEU32Codec {
@@ -14,7 +16,7 @@ impl<'a> heed::BytesDecode<'a> for StrBEU32Codec {
         let footer_len = size_of::<u32>();
 
         if bytes.len() < footer_len {
-            return Err(BoxedError::from("cannot extract footer from bytes"));
+            return Err(SliceTooShortError.into());
         }
 
         let (word, bytes) = bytes.split_at(bytes.len() - footer_len);
@@ -48,7 +50,7 @@ impl<'a> heed::BytesDecode<'a> for StrBEU16Codec {
         let footer_len = size_of::<u16>();
 
         if bytes.len() < footer_len + 1 {
-            return Err(BoxedError::from("cannot extract footer from bytes"));
+            return Err(SliceTooShortError.into());
         }
 
         let (word_plus_nul_byte, bytes) = bytes.split_at(bytes.len() - footer_len);
diff --git a/milli/src/heed_codec/str_str_u8_codec.rs b/milli/src/heed_codec/str_str_u8_codec.rs
index 743ddb1f7..0aedf0c94 100644
--- a/milli/src/heed_codec/str_str_u8_codec.rs
+++ b/milli/src/heed_codec/str_str_u8_codec.rs
@@ -1,24 +1,22 @@
 use std::borrow::Cow;
+use std::ffi::CStr;
 use std::str;
 
 use heed::BoxedError;
 
+use super::SliceTooShortError;
+
 pub struct U8StrStrCodec;
 
 impl<'a> heed::BytesDecode<'a> for U8StrStrCodec {
     type DItem = (u8, &'a str, &'a str);
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
-        let (n, bytes) = bytes.split_first().ok_or("not enough bytes").map_err(BoxedError::from)?;
-        let s1_end = bytes
-            .iter()
-            .position(|b| *b == 0)
-            .ok_or("cannot find nul byte")
-            .map_err(BoxedError::from)?;
-        let (s1_bytes, rest) = bytes.split_at(s1_end);
-        let s2_bytes = &rest[1..];
-        let s1 = str::from_utf8(s1_bytes)?;
-        let s2 = str::from_utf8(s2_bytes)?;
+        let (n, bytes) = bytes.split_first().ok_or(SliceTooShortError)?;
+        let cstr = CStr::from_bytes_until_nul(bytes)?;
+        let s1 = cstr.to_str()?;
+        // skip '\0' byte between the two strings.
+        let s2 = str::from_utf8(&bytes[s1.len() + 1..])?;
         Ok((*n, s1, s2))
     }
 }
@@ -41,14 +39,11 @@ impl<'a> heed::BytesDecode<'a> for UncheckedU8StrStrCodec {
     type DItem = (u8, &'a [u8], &'a [u8]);
 
     fn bytes_decode(bytes: &'a [u8]) -> Result<Self::DItem, BoxedError> {
-        let (n, bytes) = bytes.split_first().ok_or("not enough bytes").map_err(BoxedError::from)?;
-        let s1_end = bytes
-            .iter()
-            .position(|b| *b == 0)
-            .ok_or("cannot find nul byte")
-            .map_err(BoxedError::from)?;
-        let (s1_bytes, rest) = bytes.split_at(s1_end);
-        let s2_bytes = &rest[1..];
+        let (n, bytes) = bytes.split_first().ok_or(SliceTooShortError)?;
+        let cstr = CStr::from_bytes_until_nul(bytes)?;
+        let s1_bytes = cstr.to_bytes();
+        // skip '\0' byte between the two strings.
+        let s2_bytes = &bytes[s1_bytes.len() + 1..];
         Ok((*n, s1_bytes, s2_bytes))
     }
 }