diff --git a/pack-bitmap.c b/pack-bitmap.c
index 36134222d7a..e22bbbdc60e 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -82,6 +82,12 @@ struct bitmap_index {
 	/* The checksum of the packfile or MIDX; points into map. */
 	const unsigned char *checksum;
 
+	/*
+	 * If not NULL, this point into the commit table extension
+	 * (within the memory mapped region `map`).
+	 */
+	unsigned char *table_lookup;
+
 	/*
 	 * Extended index.
 	 *
@@ -185,6 +191,16 @@ static int load_bitmap_header(struct bitmap_index *index)
 			index->hashes = (void *)(index_end - cache_size);
 			index_end -= cache_size;
 		}
+
+		if (flags & BITMAP_OPT_LOOKUP_TABLE) {
+			size_t table_size = st_mult(ntohl(header->entry_count),
+						    BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH);
+			if (table_size > index_end - index->map - header_size)
+				return error(_("corrupted bitmap index file (too short to fit lookup table)"));
+			if (git_env_bool("GIT_TEST_READ_COMMIT_TABLE", 1))
+				index->table_lookup = (void *)(index_end - table_size);
+			index_end -= table_size;
+		}
 	}
 
 	index->entry_count = ntohl(header->entry_count);
@@ -211,11 +227,13 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 
 	hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);
 
-	/* a 0 return code means the insertion succeeded with no changes,
-	 * because the SHA1 already existed on the map. this is bad, there
-	 * shouldn't be duplicated commits in the index */
+	/*
+	 * A 0 return code means the insertion succeeded with no changes,
+	 * because the SHA1 already existed on the map. This is bad, there
+	 * shouldn't be duplicated commits in the index.
+	 */
 	if (ret == 0) {
-		error("Duplicate entry in bitmap index: %s", oid_to_hex(oid));
+		error(_("duplicate entry in bitmap index: %s"), oid_to_hex(oid));
 		return NULL;
 	}
 
@@ -470,7 +488,7 @@ static int load_bitmap(struct bitmap_index *bitmap_git)
 		!(bitmap_git->tags = read_bitmap_1(bitmap_git)))
 		goto failed;
 
-	if (load_bitmap_entries_v1(bitmap_git) < 0)
+	if (!bitmap_git->table_lookup && load_bitmap_entries_v1(bitmap_git) < 0)
 		goto failed;
 
 	return 0;
@@ -557,13 +575,229 @@ struct include_data {
 	struct bitmap *seen;
 };
 
+struct bitmap_lookup_table_triplet {
+	uint32_t commit_pos;
+	uint64_t offset;
+	uint32_t xor_row;
+};
+
+struct bitmap_lookup_table_xor_item {
+	struct object_id oid;
+	uint64_t offset;
+};
+
+/*
+ * This function gets the raw triplet from `row`'th row in the
+ * lookup table and fills that data to the `triplet`.
+ */
+static int lookup_table_get_triplet(struct bitmap_index *bitmap_git,
+				    uint32_t pos,
+				    struct bitmap_lookup_table_triplet *triplet)
+{
+	unsigned char *p = NULL;
+	if (pos >= bitmap_git->entry_count)
+		return error(_("corrupt bitmap lookup table: triplet position out of index"));
+
+	p = bitmap_git->table_lookup + st_mult(pos, BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH);
+
+	triplet->commit_pos = get_be32(p);
+	p += sizeof(uint32_t);
+	triplet->offset = get_be64(p);
+	p += sizeof(uint64_t);
+	triplet->xor_row = get_be32(p);
+	return 0;
+}
+
+/*
+ * Searches for a matching triplet. `va` is a pointer
+ * to the wanted commit position value. `vb` points to
+ * a triplet in lookup table. The first 4 bytes of each
+ * triplet (pointed by `vb`) are compared with `*va`.
+ */
+static int triplet_cmp(const void *va, const void *vb)
+{
+
+	uint32_t a = *(uint32_t *)va;
+	uint32_t b = get_be32(vb);
+	if (a > b)
+		return 1;
+	else if (a < b)
+		return -1;
+
+	return 0;
+}
+
+static uint32_t bsearch_pos(struct bitmap_index *bitmap_git,
+			    struct object_id *oid,
+			    uint32_t *result)
+{
+	int found;
+
+	if (bitmap_is_midx(bitmap_git))
+		found = bsearch_midx(oid, bitmap_git->midx, result);
+	else
+		found = bsearch_pack(oid, bitmap_git->pack, result);
+
+	return found;
+}
+
+/*
+ * `bsearch_triplet` function searches for the raw triplet having
+ * commit position same as `commit_pos` and fills `triplet`
+ * object from the raw triplet. Returns 1 on success and 0
+ * on failure.
+ */
+static int bsearch_triplet(uint32_t *commit_pos,
+			   struct bitmap_index *bitmap_git,
+			   struct bitmap_lookup_table_triplet *triplet)
+{
+	unsigned char *p = bsearch(commit_pos, bitmap_git->table_lookup, bitmap_git->entry_count,
+				   BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH, triplet_cmp);
+
+	if (!p)
+		return 0;
+	triplet->commit_pos = get_be32(p);
+	p += sizeof(uint32_t);
+	triplet->offset = get_be64(p);
+	p += sizeof(uint64_t);
+	triplet->xor_row = get_be32(p);
+	return 1;
+}
+
+static struct stored_bitmap *lazy_bitmap_for_commit(struct bitmap_index *bitmap_git,
+					  struct commit *commit)
+{
+	uint32_t commit_pos, xor_row;
+	uint64_t offset;
+	int flags;
+	struct bitmap_lookup_table_triplet triplet;
+	struct object_id *oid = &commit->object.oid;
+	struct ewah_bitmap *bitmap;
+	struct stored_bitmap *xor_bitmap = NULL;
+
+	int found = bsearch_pos(bitmap_git, oid, &commit_pos);
+
+	if (!found)
+		return NULL;
+
+	if (!bsearch_triplet(&commit_pos, bitmap_git, &triplet))
+		return NULL;
+
+	offset = triplet.offset;
+	xor_row = triplet.xor_row;
+
+	if (xor_row != 0xffffffff) {
+		int xor_flags;
+		khiter_t hash_pos;
+		uint64_t offset_xor;
+		struct bitmap_lookup_table_xor_item *xor_items;
+		struct bitmap_lookup_table_xor_item xor_item;
+		size_t xor_items_nr = 0, xor_items_alloc = 64;
+
+		ALLOC_ARRAY(xor_items, xor_items_alloc);
+		while (xor_row != 0xffffffff) {
+			struct object_id xor_oid;
+
+			if (xor_items_nr + 1 >= bitmap_git->entry_count) {
+				free(xor_items);
+				error(_("corrupt bitmap lookup table: xor chain exceed entry count"));
+				return NULL;
+			}
+
+			if (lookup_table_get_triplet(bitmap_git, xor_row, &triplet) < 0)
+				return NULL;
+
+			offset_xor = triplet.offset;
+
+			if (nth_bitmap_object_oid(bitmap_git, &xor_oid, triplet.commit_pos) < 0) {
+				free(xor_items);
+				error(_("corrupt bitmap lookup table: commit index %u out of range"),
+					triplet.commit_pos);
+				return NULL;
+			}
+
+			hash_pos = kh_get_oid_map(bitmap_git->bitmaps, xor_oid);
+
+			/*
+			 * If desired bitmap is already stored, we don't need
+			 * to iterate further. Because we know that bitmaps
+			 * that are needed to be parsed to parse this bitmap
+			 * has already been stored. So, assign this stored bitmap
+			 * to the xor_bitmap.
+			 */
+			if (hash_pos < kh_end(bitmap_git->bitmaps) &&
+			    (xor_bitmap = kh_value(bitmap_git->bitmaps, hash_pos)))
+				break;
+
+			ALLOC_GROW(xor_items, xor_items_nr + 1, xor_items_alloc);
+			xor_items[xor_items_nr++] = (struct bitmap_lookup_table_xor_item) {.oid = xor_oid,
+											   .offset = offset_xor};
+			xor_row = triplet.xor_row;
+		}
+
+		while (xor_items_nr) {
+			xor_item = xor_items[xor_items_nr - 1];
+			offset_xor = xor_item.offset;
+
+			bitmap_git->map_pos = offset_xor;
+			if (bitmap_git->map_size - bitmap_git->map_pos < 6) {
+				error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""),
+					oid_to_hex(&xor_item.oid));
+				free(xor_items);
+				return NULL;
+			}
+
+			bitmap_git->map_pos = bitmap_git->map_pos + sizeof(uint32_t) + sizeof(uint8_t);
+			xor_flags = read_u8(bitmap_git->map, &bitmap_git->map_pos);
+			bitmap = read_bitmap_1(bitmap_git);
+
+			if (!bitmap) {
+				free(xor_items);
+				return NULL;
+			}
+
+			xor_bitmap = store_bitmap(bitmap_git, bitmap, &xor_item.oid, xor_bitmap, xor_flags);
+			xor_items_nr--;
+		}
+
+		free(xor_items);
+	}
+
+	bitmap_git->map_pos = offset;
+	if (bitmap_git->map_size - bitmap_git->map_pos < 6) {
+		error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""),
+			oid_to_hex(oid));
+		return NULL;
+	}
+
+	bitmap_git->map_pos = bitmap_git->map_pos + sizeof(uint32_t) + sizeof(uint8_t);
+	flags = read_u8(bitmap_git->map, &bitmap_git->map_pos);
+	bitmap = read_bitmap_1(bitmap_git);
+
+	if (!bitmap)
+		return NULL;
+
+	return store_bitmap(bitmap_git, bitmap, oid, xor_bitmap, flags);
+}
+
 struct ewah_bitmap *bitmap_for_commit(struct bitmap_index *bitmap_git,
 				      struct commit *commit)
 {
 	khiter_t hash_pos = kh_get_oid_map(bitmap_git->bitmaps,
 					   commit->object.oid);
-	if (hash_pos >= kh_end(bitmap_git->bitmaps))
-		return NULL;
+	if (hash_pos >= kh_end(bitmap_git->bitmaps)) {
+		struct stored_bitmap *bitmap = NULL;
+		if (!bitmap_git->table_lookup)
+			return NULL;
+
+		trace2_region_enter("pack-bitmap", "reading_lookup_table", the_repository);
+		/* NEEDSWORK: cache misses aren't recorded */
+		bitmap = lazy_bitmap_for_commit(bitmap_git, commit);
+		trace2_region_leave("pack-bitmap", "reading_lookup_table", the_repository);
+		if (!bitmap)
+			return NULL;
+		return lookup_stored_bitmap(bitmap);
+	}
 	return lookup_stored_bitmap(kh_value(bitmap_git->bitmaps, hash_pos));
 }
 
@@ -1699,8 +1933,10 @@ void test_bitmap_walk(struct rev_info *revs)
 	if (revs->pending.nr != 1)
 		die("you must specify exactly one commit to test");
 
-	fprintf(stderr, "Bitmap v%d test (%d entries loaded)\n",
-		bitmap_git->version, bitmap_git->entry_count);
+	fprintf(stderr, "Bitmap v%d test (%d entries%s)",
+		bitmap_git->version,
+		bitmap_git->entry_count,
+		bitmap_git->table_lookup ? "" : " loaded");
 
 	root = revs->pending.objects[0].item;
 	bm = bitmap_for_commit(bitmap_git, (struct commit *)root);
@@ -1753,13 +1989,23 @@ void test_bitmap_walk(struct rev_info *revs)
 
 int test_bitmap_commits(struct repository *r)
 {
-	struct bitmap_index *bitmap_git = prepare_bitmap_git(r);
 	struct object_id oid;
 	MAYBE_UNUSED void *value;
+	struct bitmap_index *bitmap_git = prepare_bitmap_git(r);
+
+	/*
+	 * As this function is only used to print bitmap selected
+	 * commits, we don't have to read the commit table.
+	 */
 
 	if (!bitmap_git)
 		die("failed to load bitmap indexes");
 
+	if (bitmap_git->table_lookup) {
+		if (load_bitmap_entries_v1(bitmap_git) < 0)
+			die(_("failed to load bitmap indexes"));
+	}
+
 	kh_foreach(bitmap_git->bitmaps, oid, value, {
 		printf("%s\n", oid_to_hex(&oid));
 	});
diff --git a/pack-bitmap.h b/pack-bitmap.h
index 67a9d0fc303..9278f71ac91 100644
--- a/pack-bitmap.h
+++ b/pack-bitmap.h
@@ -23,6 +23,15 @@ struct bitmap_disk_header {
 
 #define NEEDS_BITMAP (1u<<22)
 
+/*
+ * The width in bytes of a single triplet in the lookup table
+ * extension:
+ *     (commit_pos, offset, xor_row)
+ *
+ * whose fields ar 32-, 64-, 32- bits wide, respectively.
+ */
+#define BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH (16)
+
 enum pack_bitmap_opts {
 	BITMAP_OPT_FULL_DAG = 0x1,
 	BITMAP_OPT_HASH_CACHE = 0x4,
diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index c0607172827..7e50f8e7653 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -258,6 +258,7 @@ test_bitmap_cases () {
 
 	test_expect_success 'truncated bitmap fails gracefully (ewah)' '
 		test_config pack.writebitmaphashcache false &&
+		test_config pack.writebitmaplookuptable false &&
 		git repack -ad &&
 		git rev-list --use-bitmap-index --count --all >expect &&
 		bitmap=$(ls .git/objects/pack/*.bitmap) &&
@@ -270,6 +271,7 @@ test_bitmap_cases () {
 	'
 
 	test_expect_success 'truncated bitmap fails gracefully (cache)' '
+		git config pack.writeBitmapLookupTable '"$writeLookupTable"' &&
 		git repack -ad &&
 		git rev-list --use-bitmap-index --count --all >expect &&
 		bitmap=$(ls .git/objects/pack/*.bitmap) &&
@@ -453,4 +455,24 @@ test_expect_success 'verify writing bitmap lookup table when enabled' '
 	grep "\"label\":\"writing_lookup_table\"" trace2
 '
 
+test_expect_success 'lookup table is actually used to traverse objects' '
+	git repack -adb &&
+	GIT_TRACE2_EVENT="$(pwd)/trace3" \
+		git rev-list --use-bitmap-index --count --all &&
+	grep "\"label\":\"reading_lookup_table\"" trace3
+'
+
+test_expect_success 'truncated bitmap fails gracefully (lookup table)' '
+	test_config pack.writebitmaphashcache false &&
+	git repack -adb &&
+	git rev-list --use-bitmap-index --count --all >expect &&
+	bitmap=$(ls .git/objects/pack/*.bitmap) &&
+	test_when_finished "rm -f $bitmap" &&
+	test_copy_bytes 512 <$bitmap >$bitmap.tmp &&
+	mv -f $bitmap.tmp $bitmap &&
+	git rev-list --use-bitmap-index --count --all >actual 2>stderr &&
+	test_cmp expect actual &&
+	test_i18ngrep corrupted.bitmap.index stderr
+'
+
 test_done
