diff --git a/src/borg/key.py b/src/borg/key.py
index d3bf22b15..b7d2cf601 100644
--- a/src/borg/key.py
+++ b/src/borg/key.py
@@ -152,8 +152,7 @@ def id_hash(self, data):
 
     def compress(self, chunk):
         meta, data = chunk
-        data = meta.get('compress', self.compressor).compress(data)
-        return Chunk(data, **meta)
+        return meta.get('compress', self.compressor).compress(data)
 
     def encrypt(self, chunk):
         pass
@@ -255,8 +254,8 @@ def id_hash(self, data):
         return sha256(data).digest()
 
     def encrypt(self, chunk):
-        chunk = self.compress(chunk)
-        return b''.join([self.TYPE_STR, chunk.data])
+        data = self.compress(chunk)
+        return b''.join([self.TYPE_STR, data])
 
     def decrypt(self, id, data, decompress=True):
         if data[0] != self.TYPE:
@@ -333,10 +332,10 @@ class AESKeyBase(KeyBase):
     MAC = hmac_sha256
 
     def encrypt(self, chunk):
-        chunk = self.compress(chunk)
-        self.nonce_manager.ensure_reservation(num_aes_blocks(len(chunk.data)))
+        data = self.compress(chunk)
+        self.nonce_manager.ensure_reservation(num_aes_blocks(len(data)))
         self.enc_cipher.reset()
-        data = b''.join((self.enc_cipher.iv[8:], self.enc_cipher.encrypt(chunk.data)))
+        data = b''.join((self.enc_cipher.iv[8:], self.enc_cipher.encrypt(data)))
         assert (self.MAC is blake2b_256 and len(self.enc_hmac_key) == 128 or
                 self.MAC is hmac_sha256 and len(self.enc_hmac_key) == 32)
         hmac = self.MAC(self.enc_hmac_key, data)
@@ -745,8 +744,8 @@ class AuthenticatedKey(ID_BLAKE2b_256, RepoKey):
     STORAGE = KeyBlobStorage.REPO
 
     def encrypt(self, chunk):
-        chunk = self.compress(chunk)
-        return b''.join([self.TYPE_STR, chunk.data])
+        data = self.compress(chunk)
+        return b''.join([self.TYPE_STR, data])
 
     def decrypt(self, id, data, decompress=True):
         if data[0] != self.TYPE: