diff --git a/test/functional/mempool_persist.py b/test/functional/mempool_persist.py
--- a/test/functional/mempool_persist.py
+++ b/test/functional/mempool_persist.py
@@ -77,16 +77,19 @@
                        "Verify that node2 calculates its balance correctly "
                        "after loading wallet transactions.")
         self.stop_nodes()
-        self.start_node(0)
+        # Give this one a head-start, so we can be "extra-sure" that it didn't load anything later
         self.start_node(1)
+        self.start_node(0)
         self.start_node(2)
         # Give bitcoind a second to reload the mempool
-        time.sleep(1)
-        wait_until(lambda: len(self.nodes[0].getrawmempool()) == 5)
-        wait_until(lambda: len(self.nodes[2].getrawmempool()) == 5)
+        wait_until(lambda: len(self.nodes[0].getrawmempool()) == 5, timeout=1)
+        wait_until(lambda: len(self.nodes[2].getrawmempool()) == 5, timeout=1)
+        # The others have loaded their mempool. If node_1 loaded anything, we'd probably notice by now:
         assert_equal(len(self.nodes[1].getrawmempool()), 0)
 
         # Verify accounting of mempool transactions after restart is correct
+        # Flush mempool to wallet
+        self.nodes[2].syncwithvalidationinterfacequeue()
         assert_equal(node2_balance, self.nodes[2].getbalance())
 
         self.log.debug(
diff --git a/test/functional/wallet_zapwallettxes.py b/test/functional/wallet_zapwallettxes.py
--- a/test/functional/wallet_zapwallettxes.py
+++ b/test/functional/wallet_zapwallettxes.py
@@ -61,6 +61,8 @@
 
         wait_until(lambda: self.nodes[0].getmempoolinfo()[
                    'size'] == 1, timeout=3)
+        # Flush mempool to wallet
+        self.nodes[0].syncwithvalidationinterfacequeue()
 
         assert_equal(self.nodes[0].gettransaction(txid1)['txid'], txid1)
         assert_equal(self.nodes[0].gettransaction(txid2)['txid'], txid2)