diff --git a/src/backend/distributed/commands/database.c b/src/backend/distributed/commands/database.c
index be444e23b..bc5908629 100644
--- a/src/backend/distributed/commands/database.c
+++ b/src/backend/distributed/commands/database.c
@@ -292,7 +292,9 @@ PreprocessAlterDatabaseStmt(Node *node, const char *queryString,
 	{
 		return NIL;
 	}
-
+	/* Since ALTER TABLE SET TABLESPACE statement is not supported */
+	/* inside a transaction block, we need to send the command to the */
+	/* main database directly to make it work */
 	if (!IsSetTablespaceStatement(stmt))
 	{
 		EnsureCoordinator();