diff --git a/ChangeLog b/ChangeLog
index b1f2d809..d2ff4e18 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,12 @@
-2022-02-08  Jay Berkenbilt  <ejb@ql.org>
+2022-02-09  Jay Berkenbilt  <ejb@ql.org>
 
 	* 10.6.0: release
 
+	* Fix one more PDF doc encoding omission: 0xAD is also undefined.
+	Fixes #637.
+
+2022-02-08  Jay Berkenbilt  <ejb@ql.org>
+
 	* Bug fix: when splitting pages with --split-pages or selecting
 	pages with --pages, set the output PDF version to the maximum of
 	all the input PDF versions. This is a fix to QPDFJob. If you are
diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index d0ac13ed..c4aa3afb 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -2492,6 +2492,10 @@ QUtil::pdf_doc_to_utf8(std::string const& val)
         {
             ch_short = pdf_doc_low_to_unicode[ch - 24];
         }
+        else if (ch == 173)
+        {
+            ch_short = 0xfffd;
+        }
         result += QUtil::toUTF8(ch_short);
     }
     return result;
diff --git a/libtests/qtest/qutil/qutil.out b/libtests/qtest/qutil/qutil.out
index 8bab099b..aedf49e1 100644
--- a/libtests/qtest/qutil/qutil.out
+++ b/libtests/qtest/qutil/qutil.out
@@ -88,8 +88,8 @@ alternatives
 2: 83a9e99e
 0: 717561636b
 done alternatives
-w˘wˇwˆw˙w˝w˛w˚w˜w�w
-done low characters
+w˘wˇwˆw˙w˝w˛w˚w˜w�w�w
+done other characters
 ---- whoami
 quack1
 quack2
diff --git a/libtests/qutil.cc b/libtests/qutil.cc
index e6fc4661..2142346e 100644
--- a/libtests/qutil.cc
+++ b/libtests/qutil.cc
@@ -418,10 +418,10 @@ void transcoding_test()
     print_alternatives(utf8);
     print_alternatives("quack");
     std::cout << "done alternatives" << std::endl;
-    std::string low = QUtil::pdf_doc_to_utf8(
-        "w\030w\031w\032w\033w\034w\035w\036w\037w\177w");
-    std::cout << low << std::endl;
-    std::cout << "done low characters" << std::endl;
+    std::string other = QUtil::pdf_doc_to_utf8(
+        "w\030w\031w\032w\033w\034w\035w\036w\037w\177w\255w");
+    std::cout << other << std::endl;
+    std::cout << "done other characters" << std::endl;
 }
 
 void print_whoami(char const* str)
diff --git a/manual/release-notes.rst b/manual/release-notes.rst
index 28be7cef..13173407 100644
--- a/manual/release-notes.rst
+++ b/manual/release-notes.rst
@@ -6,7 +6,7 @@ Release Notes
 For a detailed list of changes, please see the file
 :file:`ChangeLog` in the source distribution.
 
-10.6.0: February 8, 2022
+10.6.0: February 9, 2022
   - Preparation for replacement of ``PointerHolder``
 
     The next major release of qpdf will replace ``PointerHolder`` with