diff --git a/lib/libcryptsetup.h b/lib/libcryptsetup.h
index 22d74cac..df854f00 100644
--- a/lib/libcryptsetup.h
+++ b/lib/libcryptsetup.h
@@ -2034,6 +2034,19 @@ uint64_t crypt_get_iv_offset(struct crypt_device *cd);
  */
 int crypt_get_volume_key_size(struct crypt_device *cd);
 
+/**
+ * Get size (in bytes) of old volume key for LUKS2 device in reencryption.
+ *
+ * @param cd crypt LUKS2 device handle
+ *
+ * @return old volume key size when device is in reencryption state
+ *
+ * @note For LUKS2, this function can be used only if there is at least
+ *       one keyslot assigned to old data segment. Also with reencryption
+ *       mode 'encrypt' there's no old volume key.
+ */
+int crypt_get_old_volume_key_size(struct crypt_device *cd);
+
 /**
  * Get size (in bytes) of encryption sector for crypt device.
  *
diff --git a/lib/libcryptsetup.sym b/lib/libcryptsetup.sym
index a8752507..b33d5d39 100644
--- a/lib/libcryptsetup.sym
+++ b/lib/libcryptsetup.sym
@@ -192,4 +192,5 @@ CRYPTSETUP_2.8 {
 		crypt_keyslot_context_init_by_keyring;
 		crypt_keyslot_context_init_by_vk_in_keyring;
 		crypt_reencrypt_init_by_keyslot_context;
+		crypt_get_old_volume_key_size;
 } CRYPTSETUP_2.7;
diff --git a/lib/luks2/luks2.h b/lib/luks2/luks2.h
index 1675f32b..30568dbb 100644
--- a/lib/luks2/luks2.h
+++ b/lib/luks2/luks2.h
@@ -411,6 +411,7 @@ const char *LUKS2_get_integrity(struct luks2_hdr *hdr, int segment);
 int LUKS2_get_integrity_key_size(struct luks2_hdr *hdr, int segment);
 int LUKS2_keyslot_params_default(struct crypt_device *cd, struct luks2_hdr *hdr,
 	 struct luks2_keyslot_params *params);
+int LUKS2_get_old_volume_key_size(struct luks2_hdr *hdr);
 int LUKS2_get_volume_key_size(struct luks2_hdr *hdr, int segment);
 int LUKS2_get_keyslot_stored_key_size(struct luks2_hdr *hdr, int keyslot);
 const char *LUKS2_get_keyslot_cipher(struct luks2_hdr *hdr, int keyslot, size_t *key_size);
diff --git a/lib/luks2/luks2_json_metadata.c b/lib/luks2/luks2_json_metadata.c
index 57822c27..20d5fd42 100644
--- a/lib/luks2/luks2_json_metadata.c
+++ b/lib/luks2/luks2_json_metadata.c
@@ -2461,6 +2461,19 @@ int LUKS2_get_volume_key_size(struct luks2_hdr *hdr, int segment)
 	return -1;
 }
 
+int LUKS2_get_old_volume_key_size(struct luks2_hdr *hdr)
+{
+	int old_segment;
+
+	assert(hdr);
+
+	old_segment = LUKS2_reencrypt_segment_old(hdr);
+	if (old_segment < 0)
+		return old_segment;
+
+	return LUKS2_get_volume_key_size(hdr, old_segment);
+}
+
 uint32_t LUKS2_get_sector_size(struct luks2_hdr *hdr)
 {
 	return json_segment_get_sector_size(LUKS2_get_segment_jobj(hdr, CRYPT_DEFAULT_SEGMENT));
diff --git a/lib/setup.c b/lib/setup.c
index 26277a6a..301f7bb2 100644
--- a/lib/setup.c
+++ b/lib/setup.c
@@ -6413,6 +6413,19 @@ int crypt_get_volume_key_size(struct crypt_device *cd)
 	return 0;
 }
 
+int crypt_get_old_volume_key_size(struct crypt_device *cd)
+{
+	int r = _onlyLUKS2(cd, CRYPT_CD_QUIET,
+			   CRYPT_REQUIREMENT_ONLINE_REENCRYPT | CRYPT_REQUIREMENT_OPAL);
+
+	if (r < 0)
+		return 0;
+
+	r = LUKS2_get_old_volume_key_size(&cd->u.luks2.hdr);
+
+	return r < 0 ? 0 : r;
+}
+
 int crypt_get_hw_encryption_key_size(struct crypt_device *cd)
 {
 	if (!cd || !isLUKS2(cd->type))
diff --git a/tests/api-test-2.c b/tests/api-test-2.c
index 070ba820..cf6f864e 100644
--- a/tests/api-test-2.c
+++ b/tests/api-test-2.c
@@ -4201,6 +4201,7 @@ static void Luks2Reencryption(void)
 	EQ_(getflags & CRYPT_REQUIREMENT_ONLINE_REENCRYPT, CRYPT_REQUIREMENT_ONLINE_REENCRYPT);
 
 	/* some parameters are expected to change immediately after reencryption initialization */
+	EQ_(crypt_get_old_volume_key_size(cd), 32);
 	EQ_(crypt_get_volume_key_size(cd), 64);
 	OK_(strcmp(crypt_get_cipher_mode(cd), "xts-plain64"));
 	EQ_(crypt_get_sector_size(cd), 4096);
@@ -4402,6 +4403,34 @@ static void Luks2Reencryption(void)
 	CRYPT_FREE(cd);
 	CRYPT_FREE(cd2);
 
+	/* same key size reencryption */
+	OK_(crypt_init(&cd, DMDIR L_DEVICE_OK));
+	OK_(crypt_format(cd, CRYPT_LUKS2, "aes", "cbc-essiv:sha256", NULL, NULL, 32, &params2));
+	OK_(crypt_set_pbkdf_type(cd, &pbkdf));
+	EQ_(crypt_keyslot_add_by_volume_key(cd, 0, NULL, 32, PASSPHRASE, strlen(PASSPHRASE)), 0);
+	EQ_(crypt_keyslot_add_by_key(cd, 10, NULL, 32, PASSPHRASE, strlen(PASSPHRASE), CRYPT_VOLUME_KEY_NO_SEGMENT), 10);
+	rparams = (struct crypt_params_reencrypt) {
+		.mode = CRYPT_REENCRYPT_REENCRYPT,
+		.direction = CRYPT_REENCRYPT_FORWARD,
+		.resilience = "none",
+		.flags = CRYPT_REENCRYPT_INITIALIZE_ONLY
+	};
+	rparams.luks2 = &(struct crypt_params_luks2){ .sector_size = 512 };
+	NOTFAIL_(crypt_reencrypt_init_by_passphrase(cd, NULL, PASSPHRASE, strlen(PASSPHRASE), 0, 10, "aes", "xts-plain64", &rparams), "Failed to initialize reencryption");
+	EQ_(crypt_get_volume_key_size(cd), 32);
+	EQ_(crypt_get_old_volume_key_size(cd), 32);
+	CRYPT_FREE(cd);
+
+	/* same key reencryption */
+	OK_(crypt_init(&cd, DMDIR L_DEVICE_OK));
+	OK_(crypt_format(cd, CRYPT_LUKS2, "aes", "cbc-essiv:sha256", NULL, NULL, 32, &params2));
+	OK_(crypt_set_pbkdf_type(cd, &pbkdf));
+	EQ_(crypt_keyslot_add_by_volume_key(cd, 0, NULL, 32, PASSPHRASE, strlen(PASSPHRASE)), 0);
+	NOTFAIL_(crypt_reencrypt_init_by_passphrase(cd, NULL, PASSPHRASE, strlen(PASSPHRASE), 0, 0, "aes", "xts-plain64", &rparams), "Failed to initialize reencryption");
+	EQ_(crypt_get_volume_key_size(cd), 32);
+	EQ_(crypt_get_old_volume_key_size(cd), 32);
+	CRYPT_FREE(cd);
+
 	/* data shift related tests */
 	params2.sector_size = 512;
 	OK_(crypt_init(&cd, DMDIR L_DEVICE_OK));
@@ -4517,6 +4546,8 @@ static void Luks2Reencryption(void)
 	OK_(crypt_init(&cd, DMDIR L_DEVICE_OK));
 	OK_(crypt_load(cd, CRYPT_LUKS2, NULL));
 	EQ_(crypt_reencrypt_status(cd, &retparams), CRYPT_REENCRYPT_CLEAN);
+	/* With encryption there's no old volume key */
+	EQ_(crypt_get_old_volume_key_size(cd), 0);
 	EQ_(retparams.mode, CRYPT_REENCRYPT_ENCRYPT);
 	OK_(strcmp(retparams.resilience, "datashift"));
 	EQ_(retparams.data_shift, 8192);
@@ -4632,6 +4663,7 @@ static void Luks2Reencryption(void)
 	rparams.resilience = "none";
 	rparams.max_hotzone_size = 2048;
 	OK_(crypt_reencrypt_init_by_passphrase(cd, NULL, PASSPHRASE, strlen(PASSPHRASE), 6, CRYPT_ANY_SLOT, NULL, NULL, &rparams));
+	EQ_(crypt_get_old_volume_key_size(cd), 32);
 	OK_(crypt_reencrypt_run(cd, NULL, NULL));
 	CRYPT_FREE(cd);
 	OK_(crypt_init(&cd, DMDIR L_DEVICE_OK));