diff --git a/src/honeysql/helpers.clj b/src/honeysql/helpers.clj
index 7222bad..8695a98 100644
--- a/src/honeysql/helpers.clj
+++ b/src/honeysql/helpers.clj
@@ -97,7 +97,7 @@
   (assoc m :full-join clauses))
 
 (defhelper merge-full-join [m clauses]
-  (assoc m :merge-full-join clauses))
+  (update-in m [:full-join] concat clauses))
 
 (defmethod build-clause :group-by [_ m fields]
   (assoc m :group-by (collify fields)))