diff --git a/packages/fcl-stl/src/gdeque.pp b/packages/fcl-stl/src/gdeque.pp
index 2fa9d2d443..f9010ab8ca 100644
--- a/packages/fcl-stl/src/gdeque.pp
+++ b/packages/fcl-stl/src/gdeque.pp
@@ -14,6 +14,11 @@
 
 unit gdeque;
 
+{
+  Implements a generic double ended queue.
+  (See: https://en.wikipedia.org/wiki/Double-ended_queue)
+}
+
 interface
 
 type