diff --git a/t/t0090-cache-tree.sh b/t/t0090-cache-tree.sh
index 94fcb4a78e..504334e552 100755
--- a/t/t0090-cache-tree.sh
+++ b/t/t0090-cache-tree.sh
@@ -261,13 +261,16 @@ test_expect_success 'no phantom error when switching trees' '
 '
 
 test_expect_success 'switching trees does not invalidate shared index' '
-	git update-index --split-index &&
-	>split &&
-	git add split &&
-	test-tool dump-split-index .git/index | grep -v ^own >before &&
-	git commit -m "as-is" &&
-	test-tool dump-split-index .git/index | grep -v ^own >after &&
-	test_cmp before after
+	(
+		sane_unset GIT_TEST_SPLIT_INDEX &&
+		git update-index --split-index &&
+		>split &&
+		git add split &&
+		test-tool dump-split-index .git/index | grep -v ^own >before &&
+		git commit -m "as-is" &&
+		test-tool dump-split-index .git/index | grep -v ^own >after &&
+		test_cmp before after
+	)
 '
 
 test_done
diff --git a/t/t1700-split-index.sh b/t/t1700-split-index.sh
index b3b4d83eaf..be22398a85 100755
--- a/t/t1700-split-index.sh
+++ b/t/t1700-split-index.sh
@@ -57,7 +57,7 @@ test_expect_success 'disable split index' '
 	EOF
 	test_cmp ls-files.expect ls-files.actual &&
 
-	BASE=$(test-tool dump-split-index .git/index | grep "^own" | sed "s/own/base/") &&
+	BASE=$(test-tool dump-split-index .git/index | sed -n "s/^own/base/p") &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
 	cat >expect <<-EOF &&
 	not a split index