diff --git a/tests/btcproxy.py b/tests/btcproxy.py
index 30486a22e..9f7d3d348 100644
--- a/tests/btcproxy.py
+++ b/tests/btcproxy.py
@@ -19,7 +19,7 @@ class DecimalEncoder(json.JSONEncoder):
     """
     def default(self, o):
         if isinstance(o, decimal.Decimal):
-            return str(o)
+            return "{:.8f}".format(float(o))
         return super(DecimalEncoder, self).default(o)
 
 
diff --git a/tests/test_connection.py b/tests/test_connection.py
index 5b555866a..6486b72ba 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -1108,8 +1108,11 @@ def test_fundee_forget_funding_tx_unconfirmed(node_factory, bitcoind):
 @unittest.skipIf(not DEVELOPER, "needs dev_fail")
 def test_no_fee_estimate(node_factory, bitcoind, executor):
     l1 = node_factory.get_node(start=False)
-    l1.bitcoind_cmd_override(cmd='estimatesmartfee',
-                             failscript="""echo '{ "errors": [ "Insufficient data or no feerate found" ], "blocks": 0 }'; exit 0""")
+
+    # Fail any fee estimation requests until we allow them further down
+    l1.daemon.rpcproxy.mock_rpc('estimatesmartfee', {
+        'error': {"errors": ["Insufficient data or no feerate found"], "blocks": 0}
+    })
     l1.start()
 
     l2 = node_factory.get_node()
diff --git a/tests/test_misc.py b/tests/test_misc.py
index c067930e8..282d4b522 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -858,8 +858,9 @@ def test_ipv4_and_ipv6(node_factory):
 
 def test_feerates(node_factory):
     l1 = node_factory.get_node(options={'log-level': 'io'}, start=False)
-    l1.bitcoind_cmd_override(cmd='estimatesmartfee',
-                             failscript="""echo '{ "errors": [ "Insufficient data or no feerate found" ], "blocks": 0 }'; exit 0""")
+    l1.daemon.rpcproxy.mock_rpc('estimatesmartfee', {
+        'error': {"errors": ["Insufficient data or no feerate found"], "blocks": 0}
+    })
     l1.start()
 
     # Query feerates (shouldn't give any!)
diff --git a/tests/utils.py b/tests/utils.py
index d2742a5a4..6a9d18a2b 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -623,8 +623,26 @@ class LightningNode(object):
     # it on a running daemon may not give expected result!
     def set_feerates(self, feerates, wait_for_effect=True):
         # (bitcoind returns bitcoin per kb, so these are * 4)
-        self.bitcoind_cmd_override("""case "$*" in *2\ CONSERVATIVE*) FEERATE={};; *4\ ECONOMICAL*) FEERATE={};; *100\ ECONOMICAL*) FEERATE={};; *) exit 98;; esac; echo '{{ "feerate": '$(printf 0.%08u $FEERATE)' }}'; exit 0""".format(feerates[0] * 4, feerates[1] * 4, feerates[2] * 4),
-                                   'estimatesmartfee')
+
+        def mock_estimatesmartfee(r):
+            params = r['params']
+            if params == [2, 'CONSERVATIVE']:
+                feerate = feerates[0] * 4
+            elif params == [4, 'ECONOMICAL']:
+                feerate = feerates[1] * 4
+            elif params == [100, 'ECONOMICAL']:
+                feerate = feerates[2] * 4
+            else:
+                raise ValueError()
+            return {
+                'id': r['id'],
+                'error': None,
+                'result': {
+                    'feerate': Decimal(feerate) / 10**8
+                },
+            }
+        self.daemon.rpcproxy.mock_rpc('estimatesmartfee', mock_estimatesmartfee)
+
         if wait_for_effect:
             self.daemon.wait_for_log('Feerate estimate for .* set to')