diff --git a/sim/Makefile b/sim/Makefile
index 070cef4..45fb942 100644
--- a/sim/Makefile
+++ b/sim/Makefile
@@ -1,3 +1,7 @@
+#
+# Makefile for building test benches with GHDL (the free VHDL compiler).
+#
+
 
 GHDL = ghdl
 GHDLFLAGS =