diff --git a/ChangeLog b/ChangeLog
index 5de76343..cf51c5b3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-08-17  Jay Berkenbilt  <ejb@ql.org>
+
+	* Change internal implementation of QPDF arrays to use sparse
+	arrays, which results in using much less memory for arrays with
+	large numbers of nulls. Various files have been encountered in the
+	wild that contains thousands of arrays with millions of nulls.
+	Fixes #305, #311.
+
 2019-07-03  Jay Berkenbilt  <ejb@ql.org>
 
 	* Non-compatible API change: change
diff --git a/TODO b/TODO
index f79b0ae4..a80fcebc 100644
--- a/TODO
+++ b/TODO
@@ -1,10 +1,3 @@
-Performance
-===========
-
-There is some performance problem that happens with some large files.
-Issues 305 and 311 both seem to be examples of this. Files saved in
-../misc/bugs.
-
 Fuzz Errors
 ===========
 
diff --git a/manual/qpdf-manual.xml b/manual/qpdf-manual.xml
index d5ad6466..e2544cb9 100644
--- a/manual/qpdf-manual.xml
+++ b/manual/qpdf-manual.xml
@@ -4480,6 +4480,14 @@ print "\n";
           <function>getUIntValueAsUInt</function>.
          </para>
         </listitem>
+        <listitem>
+         <para>
+          The underlying implementation of QPDF arrays has been
+          enhanced to be much more memory efficient when dealing with
+          arrays with lots of nulls. This enables qpdf to use
+          drastically less memory for certain types of files.
+         </para>
+        </listitem>
         <listitem>
          <para>
           A new helper method