--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh

@@ -50,11 +50,11 @@ run_sub_test_lib_test () {
 	shift 2
 	mkdir "$name" &&
 	(
-		# Pretend we're a test harness.  This prevents
-		# test-lib from writing the counts to a file that will
-		# later be summarized, showing spurious "failed" tests
-		HARNESS_ACTIVE=t &&
-		export HARNESS_ACTIVE &&
+		# Pretend we're not running under a test harness, whether we
+		# are or not. The test-lib output depends on the setting of
+		# this variable, so we need a stable setting under which to run
+		# the sub-test.
+		sane_unset HARNESS_ACTIVE &&