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
@@ -93,9 +93,13 @@
         # Note that common args are set in the config file (see
         # initialize_datadir)
         self.extra_args = extra_args
+        # Configuration for logging is set as command-line args rather than in the bitcoin.conf file.
+        # This means that starting a bitcoind using the temp dir to debug a failed test won't
+        # spam debug.log.
         self.default_args = [
             "-datadir=" + self.datadir,
             "-logtimemicros",
+            "-logthreadnames",
             "-debug",
             "-debugexclude=libevent",
             "-debugexclude=leveldb",