diff --git a/usr.bin/diff/diff.1 b/usr.bin/diff/diff.1
index 6351c58114e..29ee32cb8d2 100644
--- a/usr.bin/diff/diff.1
+++ b/usr.bin/diff/diff.1
@@ -748,3 +748,12 @@ A
 .Nm
 command appeared in
 .At v6 .
+The
+.Nm
+implimentation in
+.Fx 1.0
+until
+.Fx 11.4
+was GNU diff.  This was replaced in
+.Fx 12.0
+by a BSD licensed diff implimentation.  Some GNU'isms were lost in process.