diff --git a/test/functional/abc-transaction-ordering.py b/test/functional/abc-transaction-ordering.py
--- a/test/functional/abc-transaction-ordering.py
+++ b/test/functional/abc-transaction-ordering.py
@@ -145,7 +145,9 @@
             self.tip = self.blocks[number]
 
         # adds transactions to the block and updates state
-        def update_block(block_number, new_transactions=[]):
+        def update_block(block_number, new_transactions=None):
+            if new_transactions is None:
+                new_transactions = []
             block = self.blocks[block_number]
             self.add_transactions_to_block(block, new_transactions)
             old_sha256 = block.sha256
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -690,7 +690,9 @@
         return [key0, key1]
 
     # Version 2 compact blocks use wtxid in shortids (rather than txid)
-    def initialize_from_block(self, block, nonce=0, prefill_list=[0]):
+    def initialize_from_block(self, block, nonce=0, prefill_list=None):
+        if prefill_list is None:
+            prefill_list = [0]
         self.header = CBlockHeader(block)
         self.nonce = nonce
         self.prefilled_txn = [PrefilledTransaction(i, block.vtx[i])
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -45,8 +45,10 @@
         self.setup_nodes()
 
     def test_importmulti(self, req, success, error_code=None,
-                         error_message=None, warnings=[]):
+                         error_message=None, warnings=None):
         """Run importmulti and assert success"""
+        if warnings is None:
+            warnings = []
         result = self.nodes[1].importmulti([req])
         observed_warnings = []
         if 'warnings' in result[0]:
diff --git a/test/lint/lint-python-mutable-default-parameters.sh b/test/lint/lint-python-mutable-default-parameters.sh
new file mode 100755
--- /dev/null
+++ b/test/lint/lint-python-mutable-default-parameters.sh
@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2019 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+# Detect when a mutable list or dict is used as a default parameter value in a Python function.
+
+export LC_ALL=C
+EXIT_CODE=0
+OUTPUT=$(git grep -E '^\s*def [a-zA-Z0-9_]+\(.*=\s*(\[|\{)' -- "*.py")
+if [[ ${OUTPUT} != "" ]]; then
+    echo "A mutable list or dict seems to be used as default parameter value:"
+    echo
+    echo "${OUTPUT}"
+    echo
+    cat << EXAMPLE
+This is how mutable list and dict default parameter values behave:
+
+>>> def f(i, j=[], k={}):
+...     j.append(i)
+...     k[i] = True
+...     return j, k
+...
+>>> f(1)
+([1], {1: True})
+>>> f(1)
+([1, 1], {1: True})
+>>> f(2)
+([1, 1, 2], {1: True, 2: True})
+
+The intended behaviour was likely:
+
+>>> def f(i, j=None, k=None):
+...     if j is None:
+...         j = []
+...     if k is None:
+...         k = {}
+...     j.append(i)
+...     k[i] = True
+...     return j, k
+...
+>>> f(1)
+([1], {1: True})
+>>> f(1)
+([1], {1: True})
+>>> f(2)
+([2], {2: True})
+EXAMPLE
+    EXIT_CODE=1
+fi
+exit ${EXIT_CODE}