diff --git a/neqo-crypto/src/aead_null.rs b/neqo-crypto/src/aead_null.rs
index bc0174492b..28dfc204b7 100644
--- a/neqo-crypto/src/aead_null.rs
+++ b/neqo-crypto/src/aead_null.rs
@@ -42,8 +42,8 @@ impl AeadNull {
     ) -> Res<&'a [u8]> {
         let l = input.len();
         output[..l].copy_from_slice(input);
-        output[l..l + 16].copy_from_slice(AEAD_NULL_TAG);
-        Ok(&output[..l + 16])
+        output[l..l + self.expansion()].copy_from_slice(AEAD_NULL_TAG);
+        Ok(&output[..l + self.expansion()])
     }
 
     #[allow(clippy::missing_errors_doc)]
@@ -52,24 +52,18 @@ impl AeadNull {
         _count: u64,
         _aad: Range<usize>,
         input: Range<usize>,
-        _data: &mut [u8],
+        data: &mut [u8],
     ) -> Res<usize> {
-        Ok(input.len() + 16)
+        data[input.end..input.end + self.expansion()].copy_from_slice(AEAD_NULL_TAG);
+        Ok(input.len() + self.expansion())
     }
 
-    #[allow(clippy::missing_errors_doc)]
-    pub fn decrypt<'a>(
-        &self,
-        _count: u64,
-        _aad: &[u8],
-        input: &[u8],
-        output: &'a mut [u8],
-    ) -> Res<&'a [u8]> {
-        if input.len() < AEAD_NULL_TAG.len() {
+    fn decrypt_check(&self, _count: u64, _aad: &[u8], input: &[u8]) -> Res<usize> {
+        if input.len() < self.expansion() {
             return Err(Error::from(SEC_ERROR_BAD_DATA));
         }
 
-        let len_encrypted = input.len() - AEAD_NULL_TAG.len();
+        let len_encrypted = input.len() - self.expansion();
         // Check that:
         // 1) expansion is all zeros and
         // 2) if the encrypted data is also supplied that at least some values are no zero
@@ -77,12 +71,43 @@ impl AeadNull {
         if &input[len_encrypted..] == AEAD_NULL_TAG
             && (len_encrypted == 0 || input[..len_encrypted].iter().any(|x| *x != 0x0))
         {
-            output[..len_encrypted].copy_from_slice(&input[..len_encrypted]);
-            Ok(&output[..len_encrypted])
+            Ok(len_encrypted)
         } else {
             Err(Error::from(SEC_ERROR_BAD_DATA))
         }
     }
+
+    #[allow(clippy::missing_errors_doc)]
+    pub fn decrypt<'a>(
+        &self,
+        count: u64,
+        aad: &[u8],
+        input: &[u8],
+        output: &'a mut [u8],
+    ) -> Res<&'a [u8]> {
+        self.decrypt_check(count, aad, input).map(|len| {
+            output[..len].copy_from_slice(&input[..len]);
+            &output[..len]
+        })
+    }
+
+    #[allow(clippy::missing_errors_doc)]
+    pub fn decrypt_in_place<'a>(
+        &self,
+        count: u64,
+        aad: Range<usize>,
+        input: Range<usize>,
+        data: &'a mut [u8],
+    ) -> Res<&'a mut [u8]> {
+        let aad = data
+            .get(aad)
+            .ok_or_else(|| Error::from(SEC_ERROR_BAD_DATA))?;
+        let inp = data
+            .get(input.clone())
+            .ok_or_else(|| Error::from(SEC_ERROR_BAD_DATA))?;
+        self.decrypt_check(count, aad, inp)
+            .map(move |len| &mut data[input.start..input.start + len])
+    }
 }
 
 impl fmt::Debug for AeadNull {
diff --git a/neqo-transport/src/packet/mod.rs b/neqo-transport/src/packet/mod.rs
index 45955bd181..24a1b2d285 100644
--- a/neqo-transport/src/packet/mod.rs
+++ b/neqo-transport/src/packet/mod.rs
@@ -788,6 +788,7 @@ impl<'a> PublicPacket<'a> {
         self.data.len()
     }
 
+    #[must_use]
     pub fn data(&self) -> &[u8] {
         self.data
     }