diff --git a/schema/mysql-changes/upgrade_2.sql b/schema/mysql-changes/upgrade_2.sql
new file mode 100644
index 00000000..04f37333
--- /dev/null
+++ b/schema/mysql-changes/upgrade_2.sql
@@ -0,0 +1 @@
+ALTER TABLE icinga_command_argument ADD UNIQUE KEY unique_idx (command_id, argument_name);
diff --git a/schema/mysql.sql b/schema/mysql.sql
index c846f5c1..06b486a1 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -195,6 +195,7 @@ CREATE TABLE icinga_command_argument (
   set_if_format ENUM('string', 'expression', 'json') DEFAULT NULL,
   PRIMARY KEY (id),
   UNIQUE INDEX sort_idx (command_id, sort_order),
+  UNIQUE KEY unique_idx (command_id, argument_name),
   CONSTRAINT icinga_command_argument_command
     FOREIGN KEY command (command_id)
     REFERENCES icinga_command (id)