diff --git a/torba/torba/client/baseledger.py b/torba/torba/client/baseledger.py
index 6be7b883b..7f55cf88f 100644
--- a/torba/torba/client/baseledger.py
+++ b/torba/torba/client/baseledger.py
@@ -1,3 +1,4 @@
+import base64
 import os
 import asyncio
 import logging
@@ -308,12 +309,12 @@ class BaseLedger(metaclass=LedgerRegistry):
     async def initial_headers_sync(self):
         target = self.network.remote_height
         current = len(self.headers)
-        get_chunk = partial(self.network.retriable_call, self.network.get_headers, count=2000)
-        chunks = [asyncio.ensure_future(get_chunk(height)) for height in range(current, target, 2000)]
+        get_chunk = partial(self.network.retriable_call, self.network.get_headers, count=2016, b64=True)
+        chunks = [asyncio.ensure_future(get_chunk(height)) for height in range(current, target, 2016)]
         async with self.headers.checkpointed_connector() as connector:
             for chunk in chunks:
                 headers = await chunk
-                connector.connect(len(self.headers), unhexlify(headers['hex']))
+                connector.connect(len(self.headers), base64.b64decode(headers['base64']))
                 log.info("Headers sync: %s / %s", connector.tell() // self.headers.header_size, target)
 
     async def update_headers(self, height=None, headers=None, subscription_update=False):
diff --git a/torba/torba/client/basenetwork.py b/torba/torba/client/basenetwork.py
index cdf33dab2..b2a5b6878 100644
--- a/torba/torba/client/basenetwork.py
+++ b/torba/torba/client/basenetwork.py
@@ -239,9 +239,9 @@ class BaseNetwork:
         restricted = 0 > height > self.remote_height - 10
         return self.rpc('blockchain.transaction.get_merkle', [tx_hash, height], restricted)
 
-    def get_headers(self, height, count=10000):
+    def get_headers(self, height, count=10000, b64=False):
         restricted = height >= self.remote_height - 100
-        return self.rpc('blockchain.block.headers', [height, count], restricted)
+        return self.rpc('blockchain.block.headers', [height, count, 0, b64], restricted)
 
     #  --- Subscribes, history and broadcasts are always aimed towards the master client directly
     def get_history(self, address):
diff --git a/torba/torba/server/session.py b/torba/torba/server/session.py
index 6f92e894a..a45f7ede1 100644
--- a/torba/torba/server/session.py
+++ b/torba/torba/server/session.py
@@ -6,6 +6,7 @@
 # and warranty status of this software.
 
 """Classes for local RPC server and remote client TCP/SSL servers."""
+import base64
 import collections
 import asyncio
 import codecs
@@ -1007,7 +1008,7 @@ class ElectrumX(SessionBase):
         height: the header's height"""
         return await self.block_header(height)
 
-    async def block_headers(self, start_height, count, cp_height=0):
+    async def block_headers(self, start_height, count, cp_height=0, b64=False):
         """Return count concatenated block headers as hex for the main chain;
         starting at start_height.
 
@@ -1021,15 +1022,16 @@ class ElectrumX(SessionBase):
         max_size = self.MAX_CHUNK_SIZE
         count = min(count, max_size)
         headers, count = await self.db.read_headers(start_height, count)
-        result = {'hex': headers.hex(), 'count': count, 'max': max_size}
+        result = {
+            'base64' if b64 else 'hex': base64.b64encode(headers).decode() if b64 else headers.hex(),
+            'count': count,
+            'max': max_size
+        }
         if count and cp_height:
             last_height = start_height + count - 1
             result.update(await self._merkle_proof(cp_height, last_height))
         return result
 
-    async def block_headers_12(self, start_height, count):
-        return await self.block_headers(start_height, count)
-
     async def block_get_chunk(self, index):
         """Return a chunk of block headers as a hexadecimal string.
 
@@ -1270,7 +1272,7 @@ class ElectrumX(SessionBase):
             handlers.update({
                 'mempool.get_fee_histogram':
                 self.mempool.compact_fee_histogram,
-                'blockchain.block.headers': self.block_headers_12,
+                'blockchain.block.headers': self.block_headers,
                 'server.ping': self.ping,
             })