diff --git a/electrumx/server/mempool.py b/electrumx/server/mempool.py
index d71a943..67305a0 100644
--- a/electrumx/server/mempool.py
+++ b/electrumx/server/mempool.py
@@ -31,6 +31,13 @@ class MemPoolTx(object):
     size = attr.ib()
 
 
+@attr.s(slots=True)
+class MemPoolTxSummary(object):
+    hash = attr.ib()
+    fee = attr.ib()
+    has_unconfirmed_inputs = attr.ib()
+
+
 class MemPoolAPI(ABC):
     '''A concrete instance of this class is passed to the MemPool object
     and used by it to query DB and blockchain state.'''
@@ -299,7 +306,6 @@ class MemPool(object):
         Can be positive or negative.
         '''
         value = 0
-        # hashXs is a defaultdict
         if hashX in self.hashXs:
             for hash in self.hashXs[hashX]:
                 tx = self.txs[hash]
@@ -325,18 +331,12 @@ class MemPool(object):
         return result
 
     async def transaction_summaries(self, hashX):
-        '''Return a list of (tx_hash, tx_fee, unconfirmed) tuples for
-        mempool entries for the hashX.
-
-        unconfirmed is True if any txin is unconfirmed.
-        '''
-        # hashXs is a defaultdict, so use get() to query
+        '''Return a list of MemPoolTxSummary objects for the hashX.'''
         result = []
         for tx_hash in self.hashXs.get(hashX, ()):
             tx = self.txs[tx_hash]
-            unconfirmed = any(prev_hash in self.txs
-                              for prev_hash, prev_idx in tx.prevouts)
-            result.append((tx_hash, tx.fee, unconfirmed))
+            has_ui = any(hash in self.txs for hash, idx in tx.prevouts)
+            result.append(MemPoolTxSummary(tx_hash, tx.fee, has_ui))
         return result
 
     async def unordered_UTXOs(self, hashX):
@@ -347,7 +347,6 @@ class MemPool(object):
         the outputs.
         '''
         utxos = []
-        # hashXs is a defaultdict, so use get() to query
         for tx_hash in self.hashXs.get(hashX, ()):
             tx = self.txs.get(tx_hash)
             for pos, (hX, value) in enumerate(tx.out_pairs):
diff --git a/electrumx/server/session.py b/electrumx/server/session.py
index 3210741..5d6b9f3 100644
--- a/electrumx/server/session.py
+++ b/electrumx/server/session.py
@@ -779,15 +779,16 @@ class ElectrumX(SessionBase):
         Status is a hex string, but must be None if there is no history.
         '''
         # Note history is ordered and mempool unordered in electrum-server
-        # For mempool, height is -1 if unconfirmed txins, otherwise 0
-        history = await self.session_mgr.limited_history(hashX)
+        # For mempool, height is -1 if it has unconfirmed inputs, otherwise 0
+        db_history = await self.session_mgr.limited_history(hashX)
         mempool = await self.mempool.transaction_summaries(hashX)
 
-        status = ''.join('{}:{:d}:'.format(hash_to_hex_str(tx_hash), height)
-                         for tx_hash, height in history)
-        status += ''.join('{}:{:d}:'.format(hash_to_hex_str(hex_hash),
-                                            -unconfirmed)
-                          for hex_hash, tx_fee, unconfirmed in mempool)
+        status = ''.join(f'{hash_to_hex_str(tx_hash)}:'
+                         f'{height:d}:'
+                         for tx_hash, height in db_history)
+        status += ''.join(f'{hash_to_hex_str(tx.hash)}:'
+                          f'{-tx.has_unconfirmed_inputs:d}:'
+                          for tx in mempool)
         if status:
             status = sha256(status.encode()).hex()
         else:
@@ -872,11 +873,11 @@ class ElectrumX(SessionBase):
 
     async def unconfirmed_history(self, hashX):
         # Note unconfirmed history is unordered in electrum-server
-        # Height is -1 if unconfirmed txins, otherwise 0
-        mempool = await self.mempool.transaction_summaries(hashX)
-        return [{'tx_hash': hash_to_hex_str(tx_hash), 'height': -unconfirmed,
-                 'fee': fee}
-                for tx_hash, fee, unconfirmed in mempool]
+        # height is -1 if it has unconfirmed inputs, otherwise 0
+        return [{'tx_hash': hash_to_hex_str(tx.hash),
+                 'height': -tx.has_unconfirmed_inputs,
+                 'fee': tx.fee}
+                for tx in await self.mempool.transaction_summaries(hashX)]
 
     async def confirmed_and_unconfirmed_history(self, hashX):
         # Note history is ordered but unconfirmed is unordered in e-s