diff --git a/library/Director/Db/Migration.php b/library/Director/Db/Migration.php
index c85adf0b..bc7aa6d0 100644
--- a/library/Director/Db/Migration.php
+++ b/library/Director/Db/Migration.php
@@ -40,7 +40,7 @@ class Migration
 
         try {
             foreach ($queries as $query) {
-                if (preg_match('/^OPTIMIZE /i', $query)) {
+                if (preg_match('/^(?:OPTIMIZE|EXECUTE) /i', $query)) {
                     $db->query($query);
                 } else {
                     $db->exec($query);
diff --git a/schema/mysql-migrations/upgrade_124.sql b/schema/mysql-migrations/upgrade_124.sql
index 471c13c6..c7e218f4 100644
--- a/schema/mysql-migrations/upgrade_124.sql
+++ b/schema/mysql-migrations/upgrade_124.sql
@@ -1,21 +1,3 @@
-ALTER TABLE icinga_service_set
-  DROP FOREIGN KEY icinga_service_set_host;
-
-ALTER TABLE icinga_service_set
-  ADD FOREIGN KEY icinga_service_set_host (host_id)
-  REFERENCES icinga_host (id)
-  ON DELETE CASCADE
-  ON UPDATE CASCADE;
-
-ALTER TABLE icinga_service
-  DROP FOREIGN KEY icinga_service_service_set;
-
-ALTER TABLE icinga_service
-  ADD CONSTRAINT icinga_service_service_set FOREIGN KEY (service_set_id)
-    REFERENCES icinga_service_set (id)
-    ON DELETE CASCADE
-    ON UPDATE CASCADE;
-
 INSERT INTO director_schema_migration
   (schema_version, migration_time)
   VALUES (124, NOW());
diff --git a/schema/mysql-migrations/upgrade_126.sql b/schema/mysql-migrations/upgrade_126.sql
new file mode 100644
index 00000000..3df3144c
--- /dev/null
+++ b/schema/mysql-migrations/upgrade_126.sql
@@ -0,0 +1,193 @@
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT * FROM information_schema.table_constraints
+        WHERE
+            table_schema   = DATABASE()
+            AND table_name = 'icinga_service_set'
+            AND constraint_name = 'icinga_service_set_host'
+    )),
+    'ALTER TABLE icinga_service_set DROP FOREIGN KEY icinga_service_set_host',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT 1
+        FROM information_schema.statistics
+        WHERE table_schema = SCHEMA()
+            AND table_name = 'icinga_service_set'
+            AND index_name = 'icinga_service_set_host'
+    )),
+    'ALTER TABLE icinga_service_set DROP INDEX icinga_service_set_host',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT * FROM information_schema.table_constraints
+        WHERE
+            table_schema   = DATABASE()
+            AND table_name = 'icinga_service_set'
+            AND constraint_name = 'icinga_service_set_ibfk_1'
+    )),
+    'ALTER TABLE icinga_service_set DROP FOREIGN KEY icinga_service_set_ibfk_1',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT 1
+        FROM information_schema.statistics
+        WHERE table_schema = SCHEMA()
+            AND table_name = 'icinga_service_set'
+            AND index_name = 'icinga_service_set_ibfk_1'
+    )),
+    'ALTER TABLE icinga_service_set DROP INDEX icinga_service_set_ibfk_1',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT * FROM information_schema.table_constraints
+        WHERE
+            table_schema   = DATABASE()
+            AND table_name = 'icinga_service_set'
+            AND constraint_name = 'icinga_service_set_ibfk_2'
+    )),
+    'ALTER TABLE icinga_service_set DROP FOREIGN KEY icinga_service_set_ibfk_2',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT 1
+        FROM information_schema.statistics
+        WHERE table_schema = SCHEMA()
+            AND table_name = 'icinga_service_set'
+            AND index_name = 'icinga_service_set_ibfk_2'
+    )),
+    'ALTER TABLE icinga_service_set DROP INDEX icinga_service_set_ibfk_2',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT * FROM information_schema.table_constraints
+        WHERE
+            table_schema   = DATABASE()
+            AND table_name = 'icinga_service'
+            AND constraint_name = 'icinga_service_service_set'
+    )),
+    'ALTER TABLE icinga_service DROP FOREIGN KEY icinga_service_service_set',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT 1
+        FROM information_schema.statistics
+        WHERE table_schema = SCHEMA()
+            AND table_name = 'icinga_service'
+            AND index_name = 'icinga_service_service_set'
+    )),
+    'ALTER TABLE icinga_service DROP INDEX icinga_service_service_set',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT * FROM information_schema.table_constraints
+        WHERE
+            table_schema   = DATABASE()
+            AND table_name = 'icinga_service'
+            AND constraint_name = 'icinga_service_ibfk_1'
+    )),
+    'ALTER TABLE icinga_service DROP FOREIGN KEY icinga_service_ibfk_1',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+SET @stmt = (SELECT IF(
+    (SELECT EXISTS(
+        SELECT 1
+        FROM information_schema.statistics
+        WHERE table_schema = SCHEMA()
+            AND table_name = 'icinga_service'
+            AND index_name = 'icinga_service_ibfk_1'
+    )),
+    'ALTER TABLE icinga_service_set DROP INDEX icinga_service_ibfk_1',
+    'SELECT 1'
+));
+
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+SET @stmt = NULL;
+
+
+ALTER TABLE icinga_service_set
+  ADD CONSTRAINT icinga_service_set_host
+    FOREIGN KEY host (host_id)
+    REFERENCES icinga_host (id)
+    ON DELETE CASCADE
+    ON UPDATE CASCADE;
+
+ALTER TABLE icinga_service
+  ADD CONSTRAINT icinga_service_service_set
+    FOREIGN KEY service_set (service_set_id)
+    REFERENCES icinga_service_set (id)
+    ON DELETE CASCADE
+    ON UPDATE CASCADE;
+
+INSERT INTO director_schema_migration
+  (schema_version, migration_time)
+  VALUES (126, NOW());
diff --git a/schema/mysql.sql b/schema/mysql.sql
index adb65376..62e35b02 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -541,8 +541,8 @@ CREATE TABLE icinga_service_set (
   PRIMARY KEY (id),
   UNIQUE KEY object_key (object_name, host_id),
   CONSTRAINT icinga_service_set_host
-  FOREIGN KEY host (host_id)
-  REFERENCES icinga_host (id)
+    FOREIGN KEY host (host_id)
+    REFERENCES icinga_host (id)
     ON DELETE CASCADE
     ON UPDATE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
@@ -1370,4 +1370,4 @@ CREATE TABLE sync_run (
 
 INSERT INTO director_schema_migration
   (schema_version, migration_time)
-  VALUES (125, NOW());
+  VALUES (126, NOW());