diff --git a/lib/libcryptsetup.h b/lib/libcryptsetup.h
index 407defed..0a7ebdba 100644
--- a/lib/libcryptsetup.h
+++ b/lib/libcryptsetup.h
@@ -1525,6 +1525,18 @@ int crypt_keyslot_area(struct crypt_device *cd,
 	uint64_t *offset,
 	uint64_t *length);
 
+/**
+ * Get size (in bytes) of key for particular keyslot.
+ * Use for LUKS2 unbound keyslots, for other keyslots it is the same as @ref crypt_get_volume_key_size
+ *
+ * @param cd crypt device handle
+ * @param keyslot keyslot number
+ *
+ * @return volume key size or negative errno value otherwise.
+ *
+ */
+int crypt_keyslot_get_key_size(struct crypt_device *cd, int keyslot);
+
 /**
  * Get directory where mapped crypt devices are created
  *
diff --git a/lib/libcryptsetup.sym b/lib/libcryptsetup.sym
index fb5db714..c4d2c43f 100644
--- a/lib/libcryptsetup.sym
+++ b/lib/libcryptsetup.sym
@@ -90,6 +90,7 @@ CRYPTSETUP_2.0 {
 		crypt_keyslot_max;
 		crypt_keyslot_area;
 		crypt_keyslot_status;
+		crypt_keyslot_get_key_size;
 		crypt_get_dir;
 		crypt_set_debug_level;
 		crypt_log;
diff --git a/lib/setup.c b/lib/setup.c
index b2bb404b..020c5456 100644
--- a/lib/setup.c
+++ b/lib/setup.c
@@ -3782,6 +3782,23 @@ int crypt_get_volume_key_size(struct crypt_device *cd)
 	return 0;
 }
 
+int crypt_keyslot_get_key_size(struct crypt_device *cd, int keyslot)
+{
+	if (!cd || !isLUKS(cd->type))
+		return -EINVAL;
+
+	if (keyslot < 0 || keyslot >= crypt_keyslot_max(cd->type))
+		return -EINVAL;
+
+	if (isLUKS1(cd->type))
+		return cd->u.luks1.hdr.keyBytes;
+
+	if (isLUKS2(cd->type))
+		return LUKS2_get_keyslot_key_size(&cd->u.luks2.hdr, keyslot);
+
+	return -EINVAL;
+}
+
 uint64_t crypt_get_data_offset(struct crypt_device *cd)
 {
 	if (!cd)
diff --git a/tests/api-test-2.c b/tests/api-test-2.c
index da3e1922..7ec80c44 100644
--- a/tests/api-test-2.c
+++ b/tests/api-test-2.c
@@ -2332,6 +2332,13 @@ static void Luks2KeyslotAdd(void)
 	EQ_(crypt_keyslot_add_by_key(cd, 2, key2, key_size-1, PASSPHRASE1, strlen(PASSPHRASE1), CRYPT_VOLUME_KEY_NO_SEGMENT), 2);
 	EQ_(crypt_keyslot_add_by_key(cd, 3, key2, 13, PASSPHRASE1, strlen(PASSPHRASE1), CRYPT_VOLUME_KEY_NO_SEGMENT), 3);
 
+	FAIL_(crypt_keyslot_get_key_size(cd, CRYPT_ANY_SLOT), "Bad keyslot specification.");
+	EQ_(crypt_get_volume_key_size(cd), key_size);
+	EQ_(crypt_keyslot_get_key_size(cd, 0), key_size);
+	EQ_(crypt_keyslot_get_key_size(cd, 1), key_size);
+	EQ_(crypt_keyslot_get_key_size(cd, 2), key_size-1);
+	EQ_(crypt_keyslot_get_key_size(cd, 3), 13);
+
 	key_ret_len = key_size - 1;
 	FAIL_(crypt_volume_key_get(cd, CRYPT_ANY_SLOT, key_ret, &key_ret_len, PASSPHRASE1, strlen(PASSPHRASE1)), "Wrong size or fips");