diff --git a/schema/mysql-migrations/upgrade_139.sql b/schema/mysql-migrations/upgrade_139.sql
new file mode 100644
index 00000000..817244b6
--- /dev/null
+++ b/schema/mysql-migrations/upgrade_139.sql
@@ -0,0 +1,7 @@
+UPDATE import_row_modifier SET priority = id;
+
+ALTER TABLE import_row_modifier ADD UNIQUE INDEX idx_prio (source_id, priority);
+
+INSERT INTO director_schema_migration
+  (schema_version, migration_time)
+  VALUES (139, NOW());
diff --git a/schema/mysql.sql b/schema/mysql.sql
index 2ba2a20a..49c3e5dc 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -1273,6 +1273,7 @@ CREATE TABLE import_row_modifier (
   description TEXT DEFAULT NULL,
   PRIMARY KEY (id),
   KEY search_idx (property_name),
+  UNIQUE INDEX idx_prio (source_id, priority),
   CONSTRAINT row_modifier_import_source
     FOREIGN KEY source (source_id)
     REFERENCES import_source (id)
@@ -1562,4 +1563,4 @@ CREATE TABLE icinga_user_resolved_var (
 
 INSERT INTO director_schema_migration
   (schema_version, migration_time)
-  VALUES (138, NOW());
+  VALUES (139, NOW());
diff --git a/schema/pgsql-migrations/upgrade_139.sql b/schema/pgsql-migrations/upgrade_139.sql
new file mode 100644
index 00000000..705d2a95
--- /dev/null
+++ b/schema/pgsql-migrations/upgrade_139.sql
@@ -0,0 +1,9 @@
+UPDATE import_row_modifier SET priority = id;
+
+CREATE UNIQUE INDEX import_row_modifier_prio
+  ON import_row_modifier (source_id, priority);
+
+
+INSERT INTO director_schema_migration
+  (schema_version, migration_time)
+  VALUES (139, NOW());
diff --git a/schema/pgsql.sql b/schema/pgsql.sql
index 92f8f932..35400dc2 100644
--- a/schema/pgsql.sql
+++ b/schema/pgsql.sql
@@ -1416,6 +1416,8 @@ CREATE TABLE import_row_modifier (
 );
 
 CREATE INDEX import_row_modifier_search_idx ON import_row_modifier (property_name);
+CREATE UNIQUE INDEX import_row_modifier_prio
+  ON import_row_modifier (source_id, priority);
 
 
 CREATE TABLE import_row_modifier_setting (
@@ -1839,4 +1841,4 @@ CREATE INDEX user_resolved_var_schecksum ON icinga_user_resolved_var (checksum);
 
 INSERT INTO director_schema_migration
   (schema_version, migration_time)
-  VALUES (138, NOW());
+  VALUES (139, NOW());