diff --git a/docs/protocol-changes.rst b/docs/protocol-changes.rst
index 54b8d10..fc0a4fe 100644
--- a/docs/protocol-changes.rst
+++ b/docs/protocol-changes.rst
@@ -127,16 +127,19 @@ This version removes all support for :ref:`deserialized headers
 Changes
 -------
 
-  * The argument *raw* removed from :func:`blockchain.headers.subscribe`,
-    only raw headers can be subscribed to.
+  * Deserialized headers are no longer available, so removed argument
+    *raw* from :func:`blockchain.headers.subscribe`.
   * Only the first :func:`server.version` message is accepted.
   * Optional *cp_height* argument added to
     :func:`blockchain.block.header` and :func:`blockchain.block.headers`
+    to return merkle proofs of the header to a given checkpoint.
 
 New methods
 -----------
 
-  * :func:`blockchain.transaction.id_from_pos`
+  * :func:`blockchain.transaction.id_from_pos` to return a transaction
+    hash, and optionally a merkle proof, given a block height and
+    position in the block.
 
 Removed methods
 ---------------
diff --git a/docs/protocol-methods.rst b/docs/protocol-methods.rst
index c1cc056..96e6666 100644
--- a/docs/protocol-methods.rst
+++ b/docs/protocol-methods.rst
@@ -679,12 +679,13 @@ given a block height and a position in the block.
 
 **Signature**
 
-  .. function:: blockchain.transaction.id_from_pos(height, tx_pos, merkle=False)
+  .. function:: blockchain.transaction.id_from_pos(height, tx_pos,
+                merkle=False)
   .. versionadded:: 1.4
 
   *height*
 
-    A block height in the main chain, an integer.
+    The main chain block height, a non-negative integer.
 
   *tx_pos*
 
diff --git a/electrumx/server/session.py b/electrumx/server/session.py
index 4412697..3267b8b 100644
--- a/electrumx/server/session.py
+++ b/electrumx/server/session.py
@@ -1055,7 +1055,7 @@ class ElectrumX(SessionBase):
 
         return await self.daemon_request('getrawtransaction', tx_hash, verbose)
 
-    async def block_hash_and_tx_hashes(self, height):
+    async def _block_hash_and_tx_hashes(self, height):
         '''Returns a pair (block_hash, tx_hashes) for the main chain block at
         the given height.
 
@@ -1080,14 +1080,14 @@ class ElectrumX(SessionBase):
         return branch
 
     async def transaction_merkle(self, tx_hash, height):
-        '''Return the markle tree to a confirmed transaction given its hash
+        '''Return the markle branch to a confirmed transaction given its hash
         and height.
 
         tx_hash: the transaction hash as a hexadecimal string
         height: the height of the block it is in
         '''
         assert_tx_hash(tx_hash)
-        block_hash, tx_hashes = await self.block_hash_and_tx_hashes(height)
+        block_hash, tx_hashes = await self._block_hash_and_tx_hashes(height)
         try:
             pos = tx_hashes.index(tx_hash)
         except ValueError:
@@ -1104,15 +1104,15 @@ class ElectrumX(SessionBase):
         if merkle not in (True, False):
             raise RPCError(BAD_REQUEST, f'"merkle" must be a boolean')
 
-        block_hash, tx_hashes = await self.block_hash_and_tx_hashes(height)
+        block_hash, tx_hashes = await self._block_hash_and_tx_hashes(height)
         try:
             tx_hash = tx_hashes[tx_pos]
         except IndexError:
             raise RPCError(BAD_REQUEST, f'no tx at position {tx_pos:,d} in '
                            f'block {block_hash} at height {height:,d}')
-        branch = self._get_merkle_branch(tx_hashes, tx_pos)
 
         if merkle:
+            branch = self._get_merkle_branch(tx_hashes, tx_pos)
             return {"tx_hash": tx_hash, "merkle": branch}
         else:
             return tx_hash