diff --git a/ChangeLog b/ChangeLog
index 9ee2c08c..c83d58bd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2021-01-16  Jay Berkenbilt  <ejb@ql.org>
 
+	* Re-implement QPDFNameTreeObjectHelper and
+	QPDFNumberTreeObjectHelper to be much more efficient and to have
+	an iterator-based API in addition to the existing one. This makes
+	it possible to use "range-for" loops over these helpers and to
+	iterate through name and number trees without creating a map
+	containing all the keys and values, which is slow and potentially
+	consumes a lot of memory.
+
 	* Add warn() to QPDF's public API.
 
 2021-01-11  Jay Berkenbilt  <ejb@ql.org>
diff --git a/include/qpdf/QPDFNameTreeObjectHelper.hh b/include/qpdf/QPDFNameTreeObjectHelper.hh
index f94d34cf..e5bb2893 100644
--- a/include/qpdf/QPDFNameTreeObjectHelper.hh
+++ b/include/qpdf/QPDFNameTreeObjectHelper.hh
@@ -53,7 +53,7 @@ class QPDFNameTreeObjectHelper: public QPDFObjectHelper
     bool hasName(std::string const& utf8);
 
     // Find an object by name. If found, returns true and initializes
-    // oh.
+    // oh. See also find().
     QPDF_DLL
     bool findObject(std::string const& utf8, QPDFObjectHandle& oh);
 
diff --git a/include/qpdf/QPDFNumberTreeObjectHelper.hh b/include/qpdf/QPDFNumberTreeObjectHelper.hh
index 393e8dba..d4e93690 100644
--- a/include/qpdf/QPDFNumberTreeObjectHelper.hh
+++ b/include/qpdf/QPDFNumberTreeObjectHelper.hh
@@ -60,7 +60,7 @@ class QPDFNumberTreeObjectHelper: public QPDFObjectHelper
     bool hasIndex(numtree_number idx);
 
     // Find an object with a specific index. If found, returns true
-    // and initializes oh.
+    // and initializes oh. See also find().
     QPDF_DLL
     bool findObject(numtree_number idx, QPDFObjectHandle& oh);
     // Find the object at the index or, if not found, the object whose
@@ -70,7 +70,8 @@ class QPDFNumberTreeObjectHelper: public QPDFObjectHelper
     // offset to the difference between the requested index and the
     // actual index. For example, if a number tree has values for 3
     // and 6 and idx is 5, this method would return true, initialize
-    // oh to the value with index 3, and set offset to 2 (5 - 3).
+    // oh to the value with index 3, and set offset to 2 (5 - 3). See
+    // also find().
     QPDF_DLL
     bool findObjectAtOrBelow(numtree_number idx, QPDFObjectHandle& oh,
                              numtree_number& offset);
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 647e94c2..5b590525 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -3011,8 +3011,7 @@ QPDF::findAttachmentStreams()
         return;
     }
     QPDFNameTreeObjectHelper ef_tree(embedded_files);
-    auto ef_tree_map = ef_tree.getAsMap();
-    for (auto& i: ef_tree_map)
+    for (auto i: ef_tree)
     {
         QPDFObjectHandle item = i.second;
         if (item.isDictionary() &&
diff --git a/manual/qpdf-manual.xml b/manual/qpdf-manual.xml
index e770c3c4..a969ce32 100644
--- a/manual/qpdf-manual.xml
+++ b/manual/qpdf-manual.xml
@@ -4833,6 +4833,13 @@ print "\n";
           <classname>QPDF</classname>'s public API.
          </para>
         </listitem>
+        <listitem>
+         <para>
+          Re-implement <classname>QPDFNameTreeObjectHelper</classname>
+          and <classname>QPDFNumberTreeObjectHelper</classname> to be
+          more efficient, and add an iterator-based API.
+         </para>
+        </listitem>
        </itemizedlist>
       </listitem>
      </itemizedlist>