diff --git a/test/functional/bip68-sequence.py b/test/functional/bip68-sequence.py
--- a/test/functional/bip68-sequence.py
+++ b/test/functional/bip68-sequence.py
@@ -287,7 +287,7 @@
 
         # Mine tx2, and then try again
         self.nodes[0].prioritisetransaction(
-            tx2.hash, 1e15, int(self.relayfee * COIN))
+            tx2.hash, 1e15, self.nodes[0].calculate_fee(tx2))
 
         # Advance the time on the node so that we can test timelocks
         self.nodes[0].setmocktime(cur_time + 600)
diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -13,6 +13,7 @@
 import subprocess
 import time
 
+from .mininode import COIN, ToHex
 from .util import (
     assert_equal,
     get_rpc_proxy,
@@ -64,6 +65,7 @@
         self.rpc_connected = False
         self.rpc = None
         self.url = None
+        self.relay_fee_cache = None
         self.log = logging.getLogger('TestFramework.node%d' % i)
 
     def __getattr__(self, *args, **kwargs):
@@ -156,6 +158,15 @@
         self.encryptwallet(passphrase)
         self.wait_until_stopped()
 
+    def relay_fee(self, cached=True):
+        if not self.relay_fee_cache or not cached:
+            self.relay_fee_cache = self.getnetworkinfo()["relayfee"]
+
+        return self.relay_fee_cache
+
+    def calculate_fee(self, tx):
+        return int(self.relay_fee() * len(ToHex(tx)) * COIN)
+
 
 class TestNodeCLI():
     """Interface to bitcoin-cli for an individual node"""