diff --git a/plugins/libkolab/SQL/mysql.initial.sql b/plugins/libkolab/SQL/mysql.initial.sql
index 4f4f5262..0213c45b 100644
--- a/plugins/libkolab/SQL/mysql.initial.sql
+++ b/plugins/libkolab/SQL/mysql.initial.sql
@@ -29,7 +29,7 @@ DROP TABLE IF EXISTS `kolab_cache_contact`;
 CREATE TABLE `kolab_cache_contact` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -53,7 +53,7 @@ DROP TABLE IF EXISTS `kolab_cache_event`;
 CREATE TABLE `kolab_cache_event` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -73,7 +73,7 @@ DROP TABLE IF EXISTS `kolab_cache_task`;
 CREATE TABLE `kolab_cache_task` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -93,7 +93,7 @@ DROP TABLE IF EXISTS `kolab_cache_journal`;
 CREATE TABLE `kolab_cache_journal` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -113,7 +113,7 @@ DROP TABLE IF EXISTS `kolab_cache_note`;
 CREATE TABLE `kolab_cache_note` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -131,7 +131,7 @@ DROP TABLE IF EXISTS `kolab_cache_file`;
 CREATE TABLE `kolab_cache_file` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -151,7 +151,7 @@ DROP TABLE IF EXISTS `kolab_cache_configuration`;
 CREATE TABLE `kolab_cache_configuration` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -171,7 +171,7 @@ DROP TABLE IF EXISTS `kolab_cache_freebusy`;
 CREATE TABLE `kolab_cache_freebusy` (
   `folder_id` BIGINT UNSIGNED NOT NULL,
   `msguid` BIGINT UNSIGNED NOT NULL,
-  `uid` VARCHAR(512) CHARACTER SET ascii NOT NULL,
+  `uid` VARCHAR(512) NOT NULL,
   `created` DATETIME DEFAULT NULL,
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
@@ -188,4 +188,4 @@ CREATE TABLE `kolab_cache_freebusy` (
 
 /*!40014  SET FOREIGN_KEY_CHECKS=1 */;
 
-REPLACE INTO `system` (`name`, `value`) VALUES ('libkolab-version', '2017071900');
+REPLACE INTO `system` (`name`, `value`) VALUES ('libkolab-version', '2018021300');
diff --git a/plugins/libkolab/SQL/mysql/2018021300.sql b/plugins/libkolab/SQL/mysql/2018021300.sql
new file mode 100644
index 00000000..9b5981d1
--- /dev/null
+++ b/plugins/libkolab/SQL/mysql/2018021300.sql
@@ -0,0 +1,9 @@
+-- accept utf8 in UID column
+ALTER TABLE `kolab_cache_contact` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_event` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_task` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_journal` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_note` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_file` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_configuration` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
+ALTER TABLE `kolab_cache_freebusy` MODIFY `uid` VARCHAR(512) CHARACTER SET utf8 NOT NULL;
diff --git a/plugins/libkolab/SQL/oracle.initial.sql b/plugins/libkolab/SQL/oracle.initial.sql
index 77a16ee3..78675783 100644
--- a/plugins/libkolab/SQL/oracle.initial.sql
+++ b/plugins/libkolab/SQL/oracle.initial.sql
@@ -183,4 +183,4 @@ CREATE TABLE "kolab_cache_freebusy" (
 CREATE INDEX "kolab_cache_fb_uid2msguid" ON "kolab_cache_freebusy" ("folder_id", "uid", "msguid");
 
 
-INSERT INTO "system" ("name", "value") VALUES ('libkolab-version', '2017071900');
+INSERT INTO "system" ("name", "value") VALUES ('libkolab-version', '2018021300');
diff --git a/plugins/libkolab/SQL/oracle/2018021300.sql b/plugins/libkolab/SQL/oracle/2018021300.sql
new file mode 100644
index 00000000..fe6741a0
--- /dev/null
+++ b/plugins/libkolab/SQL/oracle/2018021300.sql
@@ -0,0 +1 @@
+-- empty
\ No newline at end of file
diff --git a/plugins/libkolab/SQL/sqlite.initial.sql b/plugins/libkolab/SQL/sqlite.initial.sql
index 7a56636f..909188ca 100644
--- a/plugins/libkolab/SQL/sqlite.initial.sql
+++ b/plugins/libkolab/SQL/sqlite.initial.sql
@@ -156,4 +156,4 @@ CREATE TABLE kolab_cache_freebusy (
 
 CREATE INDEX ix_freebusy_uid2msguid ON kolab_cache_freebusy(folder_id,uid,msguid);
 
-INSERT INTO system (name, value) VALUES ('libkolab-version', '2017071900');
+INSERT INTO system (name, value) VALUES ('libkolab-version', '2018021300');
diff --git a/plugins/libkolab/SQL/sqlite/2018021300.sql b/plugins/libkolab/SQL/sqlite/2018021300.sql
new file mode 100644
index 00000000..fe6741a0
--- /dev/null
+++ b/plugins/libkolab/SQL/sqlite/2018021300.sql
@@ -0,0 +1 @@
+-- empty
\ No newline at end of file