diff --git a/pack-bitmap.c b/pack-bitmap.c
index e8a82945cc..9c9b27b723 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -1559,7 +1559,7 @@ static struct bitmap *find_objects(struct bitmap_index *bitmap_git,
 
 		if (base) {
 			int pos = bitmap_position(bitmap_git, &object->oid);
-			if (pos > 0 && bitmap_get(base, pos)) {
+			if (pos >= 0 && bitmap_get(base, pos)) {
 				object->flags |= SEEN;
 				continue;
 			}
diff --git a/t/t5333-pseudo-merge-bitmaps.sh b/t/t5333-pseudo-merge-bitmaps.sh
index 305d677108..5b2a17f90a 100755
--- a/t/t5333-pseudo-merge-bitmaps.sh
+++ b/t/t5333-pseudo-merge-bitmaps.sh
@@ -50,7 +50,15 @@ test_expect_success 'bitmap traversal without pseudo-merges' '
 	test_pseudo_merges_cascades 0 <trace2.txt &&
 	test_pseudo_merges >merges &&
 	test_must_be_empty merges &&
-	test_cmp expect actual
+	test_cmp expect actual &&
+
+	: >trace2.txt &&
+	GIT_TRACE2_EVENT=$PWD/trace2.txt \
+		git rev-list --objects --use-bitmap-index HEAD HEAD >/dev/null &&
+
+	# The first HEAD initializes base from its position-zero bitmap. The
+	# duplicate root should not count as another bitmap hit.
+	test_trace2_data bitmap bitmap/hits 1 <trace2.txt
 '
 
 test_expect_success 'pseudo-merges accurately represent their objects' '
@@ -85,6 +93,10 @@ test_expect_success 'bitmap traversal with pseudo-merges' '
 
 	test_pseudo_merges_satisfied 8 <trace2.txt &&
 	test_pseudo_merges_cascades 1 <trace2.txt &&
+
+	# Position zero is named by HEAD, its branch, and its tag, but it
+	# should count as only one bitmap hit.
+	test_trace2_data bitmap bitmap/hits 1 <trace2.txt &&
 	test_cmp expect actual
 '