diff --git a/t/t9210-scalar.sh b/t/t9210-scalar.sh
index 009437a5f3..f2a6df77ce 100755
--- a/t/t9210-scalar.sh
+++ b/t/t9210-scalar.sh
@@ -152,6 +152,10 @@ test_expect_success 'set up repository to clone' '
 '
 
 test_expect_success 'scalar clone' '
+	# index.skipHash (Scalar default) and GIT_TEST_SPLIT_INDEX are
+	# incompatible: the shared index gets a null OID and fails to
+	# load on re-read.
+	sane_unset GIT_TEST_SPLIT_INDEX &&
 	second=$(git rev-parse --verify second:second.t) &&
 	scalar clone "file://$(pwd)" cloned --single-branch &&
 	(
@@ -182,6 +186,7 @@ test_expect_success 'scalar clone' '
 '
 
 test_expect_success 'scalar clone --no-... opts' '
+	sane_unset GIT_TEST_SPLIT_INDEX &&
 	# Note: redirect stderr always to avoid having a verbose test
 	# run result in a difference in the --[no-]progress option.
 	GIT_TRACE2_EVENT="$(pwd)/no-opt-trace" scalar clone \
@@ -307,6 +312,7 @@ test_expect_success '`scalar [...] <dir>` errors out when dir is missing' '
 
 SQ="'"
 test_expect_success UNZIP 'scalar diagnose' '
+	sane_unset GIT_TEST_SPLIT_INDEX &&
 	scalar clone "file://$(pwd)" cloned --single-branch &&
 	git repack &&
 	echo "$(pwd)/.git/objects/" >>cloned/src/.git/objects/info/alternates &&
diff --git a/t/t9211-scalar-clone.sh b/t/t9211-scalar-clone.sh
index bfbf22a462..2043f48a1a 100755
--- a/t/t9211-scalar-clone.sh
+++ b/t/t9211-scalar-clone.sh
@@ -8,6 +8,11 @@ test_description='test the `scalar clone` subcommand'
 GIT_TEST_MAINT_SCHEDULER="crontab:test-tool crontab cron.txt,launchctl:true,schtasks:true"
 export GIT_TEST_MAINT_SCHEDULER
 
+# index.skipHash (Scalar default) and GIT_TEST_SPLIT_INDEX are
+# incompatible: the shared index gets a null OID and fails to
+# load on re-read.  Every test here uses scalar clone.
+sane_unset GIT_TEST_SPLIT_INDEX
+
 test_expect_success 'set up repository to clone' '
 	rm -rf .git &&
 	git init to-clone &&