diff --git a/tests/lib/libcurses/tests/addch b/tests/lib/libcurses/tests/addch
index f7e8608a7b3b..dbf5893059f1 100644
--- a/tests/lib/libcurses/tests/addch
+++ b/tests/lib/libcurses/tests/addch
@@ -1,3 +1,18 @@
+# $NetBSD: addch,v 1.7 2021/02/14 11:21:37 rillig Exp $
+#
+# Between at least 2012 and 2016, addstr did not advance win->curx for a '\t',
+# but addch did.  This was inconsistent.
+#
+# On 2016.11.28.18.25.26 on NetBSD 7.99.43, this inconsistency was fixed.
+# Now both functions advanced win->curx.
+#
+# On 2019.05.20.22.17.41 on NetBSD 8.99.41, the fix was modified, which
+# introduced another inconsistency.  Since then, addstr advanced win->curx as
+# expected, but addch advanced it by twice the amount.
+#
+# On 2021.02.13.14.30.37 on NetBSD 9.99.80, this inconsistency was fixed.
+# Now both functions advanced win->curx again.
+
 include start
 call OK addch `\001t`
 call OK refresh
@@ -5,17 +20,11 @@ call OK mvaddch 5 3 `\003e`
 call OK refresh
 call OK addch `\000\n`
 
-# Somewhere between NetBSD 8.0 and 9.0, a bug was added to addch that
-# doubled the spaces for a tab.  Instead of 8 spaces, there were 16.
-# Fixed in NetBSD 9.99.80.
 call OK addch `\000\t`
 call2 6 8 getyx STDSCR
 call OK addch `\0008`
 call OK addch `\000\n`
 
-# Somewhere between NetBSD 8.0 and 9.0, a bug was added to addch that
-# doubled the spaces for a tab.  Instead of 1 space, there were 2.
-# Fixed in NetBSD 9.99.80.
 call OK addstr "0123456"
 call OK addch `\000\t`
 call2 7 8 getyx STDSCR