diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index f62bcbf2b140d1..3078787115f9f1 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -485,6 +485,13 @@ static int try_bitmap_traversal(struct rev_info *revs,
 	if (revs->max_count >= 0)
 		return -1;
 
+	/*
+	 * We can't know which commits were left/right in a single traversal,
+	 * and we don't yet know how to traverse them separately.
+	 */
+	if (revs->left_right)
+		return -1;
+
 	bitmap_git = prepare_bitmap_walk(revs, filter_provided_objects);
 	if (!bitmap_git)
 		return -1;
diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index 7044c7d7c6d0bc..6bcbea64cc396a 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -503,6 +503,18 @@ test_expect_success 'boundary-based traversal is used when requested' '
 	done
 '
 
+test_expect_success 'left-right not confused by bitmap index' '
+	git rev-list --left-right other...HEAD >expect &&
+	git rev-list --use-bitmap-index --left-right other...HEAD >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'left-right count not confused by bitmap-index' '
+	git rev-list --left-right --count other...HEAD >expect &&
+	git rev-list --use-bitmap-index --left-right --count other...HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_bitmap_cases "pack.writeBitmapLookupTable"
 
 test_expect_success 'verify writing bitmap lookup table when enabled' '