diff --git a/contrib/pyln-testing/pyln/testing/utils.py b/contrib/pyln-testing/pyln/testing/utils.py
index a5350ce4c..fb62c1ecd 100644
--- a/contrib/pyln-testing/pyln/testing/utils.py
+++ b/contrib/pyln-testing/pyln/testing/utils.py
@@ -489,6 +489,9 @@ class LightningD(TailableProc):
             'ignore-fee-limits': 'false',
             'bitcoin-rpcuser': BITCOIND_CONFIG['rpcuser'],
             'bitcoin-rpcpassword': BITCOIND_CONFIG['rpcpassword'],
+
+            # Make sure we don't touch any existing config files in the user's $HOME
+            'bitcoin-datadir': lightning_dir,
         }
 
         for k, v in opts.items():
diff --git a/tests/plugins/bitcoin/part1.py b/tests/plugins/bitcoin/part1.py
index 24cd61fb2..fdd759cb5 100755
--- a/tests/plugins/bitcoin/part1.py
+++ b/tests/plugins/bitcoin/part1.py
@@ -33,5 +33,6 @@ def getchaininfo(plugin, **kwargs):
 plugin.add_option("bitcoin-rpcuser", "", "")
 plugin.add_option("bitcoin-rpcpassword", "", "")
 plugin.add_option("bitcoin-rpcport", "", "")
+plugin.add_option("bitcoin-datadir", "", "")
 
 plugin.run()