diff --git a/migrations/093_unique_username_constraint.rb b/migrations/093_unique_username_constraint.rb
new file mode 100644
index 00000000..265394dc
--- /dev/null
+++ b/migrations/093_unique_username_constraint.rb
@@ -0,0 +1,8 @@
+Sequel.migration do
+  up {
+    DB['ALTER TABLE sites ADD CONSTRAINT uniqueusername UNIQUE (username)'].first
+  }
+
+  down {
+  }
+end