diff --git a/schema/mysql-migrations/upgrade_188.sql b/schema/mysql-migrations/upgrade_188.sql
new file mode 100644
index 000000000..764215185
--- /dev/null
+++ b/schema/mysql-migrations/upgrade_188.sql
@@ -0,0 +1,14 @@
+ALTER TABLE director_activity_log
+DROP INDEX checksum,
+ADD UNIQUE INDEX checksum (checksum);
+
+ALTER TABLE director_generated_config
+ADD CONSTRAINT director_generated_config_activity
+    FOREIGN KEY (last_activity_checksum)
+    REFERENCES director_activity_log (checksum)
+    ON DELETE RESTRICT
+    ON UPDATE RESTRICT;
+
+INSERT INTO director_schema_migration
+  (schema_version, migration_time)
+  VALUES (188, NOW());
diff --git a/schema/mysql.sql b/schema/mysql.sql
index 832ab122d..dd8a0f849 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -46,7 +46,7 @@ CREATE TABLE director_activity_log (
   INDEX search_idx (object_name),
   INDEX search_idx2 (object_type(32), object_name(64), change_time),
   INDEX search_author (author),
-  INDEX checksum (checksum)
+  UNIQUE INDEX checksum (checksum)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 CREATE TABLE director_activity_log_remark (
@@ -114,7 +114,7 @@ CREATE TABLE director_generated_config (
   last_activity_checksum VARBINARY(20) NOT NULL,
   PRIMARY KEY (checksum),
   CONSTRAINT director_generated_config_activity
-    FOREIGN KEY activity_checksum (last_activity_checksum)
+    FOREIGN KEY (last_activity_checksum)
     REFERENCES director_activity_log (checksum)
     ON DELETE RESTRICT
     ON UPDATE RESTRICT
@@ -2446,4 +2446,4 @@ CREATE TABLE branched_icinga_dependency (
 
 INSERT INTO director_schema_migration
   (schema_version, migration_time)
-  VALUES (187, NOW());
+  VALUES (188, NOW());