diff --git a/ChangeLog b/ChangeLog
index 8821833..19b79c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-08-07  Bruno Haible  <bruno@clisp.org>
 
+	* tests/check-subst: Add comments about OSF/1.
+
+2011-08-07  Bruno Haible  <bruno@clisp.org>
+
 	* lib/relocatable.c: Update from gnulib.
 
 2011-08-06  Bruno Haible  <bruno@clisp.org>
diff --git a/tests/check-subst b/tests/check-subst
index 67339a9..287571b 100755
--- a/tests/check-subst
+++ b/tests/check-subst
@@ -53,6 +53,7 @@
 $iconv --byte-subst='<0x%010000x>' -f ASCII -t ASCII < tmp-in > tmp-out
 # This printf command crashes on Solaris 10.
 # See <http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6550204>.
+# Likewise on OSF/1 5.1.
 if printf 'B<0x%010000x><0x%010000x>se B<0x%010000x><0x%010000x>bchen\n' 0xC3 0xB6 0xC3 0xBC > tmp-ok 2>/dev/null; then
   cmp tmp-out tmp-ok
 fi
@@ -109,6 +110,7 @@
 $iconv --byte-subst='<0x%010000x>' -f ASCII -t ASCII < tmp-in > tmp-out
 # This printf command crashes on Solaris 10.
 # See <http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6550204>.
+# Likewise on OSF/1 5.1.
 if printf 'B<0x%010000x><0x%010000x>se B<0x%010000x><0x%010000x>bchen\n' 0xC3 0xB6 0xC3 0xBC > tmp-ok 2>/dev/null; then
   cmp tmp-out tmp-ok
 fi