diff --git a/jOOQ/src/main/java/org/jooq/impl/Union.java b/jOOQ/src/main/java/org/jooq/impl/Union.java
index b793ff42e9..a99a59b995 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Union.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Union.java
@@ -94,11 +94,12 @@ class Union<R extends Record> extends AbstractSelect<R> {
 
     private final void wrappingParenthesis(RenderContext context, String parenthesis) {
         switch (context.getDialect()) {
-            // Sybase ASE, SQLite and DERBY have some syntax issues with unions.
+            // Sybase ASE, Derby, Firebird and SQLite have some syntax issues with unions.
             // Check out https://issues.apache.org/jira/browse/DERBY-2374
-            case SQLITE:
-            case DERBY:
             case ASE:
+            case DERBY:
+            case FIREBIRD:
+            case SQLITE:
 
             // [#288] MySQL has a very special way of dealing with UNION's
             // So include it as well