diff --git a/src/node/handler/PadMessageHandler.js b/src/node/handler/PadMessageHandler.js
index 3c04e151a6b..7189898a79d 100644
--- a/src/node/handler/PadMessageHandler.js
+++ b/src/node/handler/PadMessageHandler.js
@@ -654,11 +654,12 @@ const handleUserChanges = async (socket, message) => {
 
     const prevText = pad.text();
 
-    if (Changeset.oldLen(changeset) !== prevText.length) {
+    if (Changeset.unpack(changeset).oldLen !== prevText.length) {
       socket.json.send({disconnect: 'badChangeset'});
       stats.meter('failedChangesets').mark();
-      throw new Error(`Can't apply USER_CHANGES ${changeset} with oldLen ` +
-                      `${Changeset.oldLen(changeset)} to document of length ${prevText.length}`);
+      throw new Error(
+          `Can't apply USER_CHANGES ${changeset} with oldLen ` +
+          `${Changeset.unpack(changeset).oldLen} to document of length ${prevText.length}`);
     }
 
     try {
diff --git a/src/static/js/Changeset.js b/src/static/js/Changeset.js
index 908cbdb35bf..824ca3810c1 100644
--- a/src/static/js/Changeset.js
+++ b/src/static/js/Changeset.js
@@ -246,18 +246,26 @@ class Changeset {
 /**
  * Returns the required length of the text before changeset can be applied.
  *
+ * @deprecated Use `Changeset.unpack(cs).oldLen` instead.
  * @param {string} cs - String representation of the Changeset
  * @returns {number} oldLen property
  */
-exports.oldLen = (cs) => Changeset.unpack(cs).oldLen;
+exports.oldLen = (cs) => {
+  warnDeprecated('Changeset.oldLen(cs) is deprecated; use Changeset.unpack(cs).oldLen instead');
+  return Changeset.unpack(cs).oldLen;
+};
 
 /**
  * Returns the length of the text after changeset is applied.
  *
+ * @deprecated Use `Changeset.unpack(cs).newLen` instead.
  * @param {string} cs - String representation of the Changeset
  * @returns {number} newLen property
  */
-exports.newLen = (cs) => Changeset.unpack(cs).newLen;
+exports.newLen = (cs) => {
+  warnDeprecated('Changeset.newLen(cs) is deprecated; use Changeset.unpack(cs).newLen instead');
+  return Changeset.unpack(cs).newLen;
+};
 
 /**
  * Iterator over a changeset's operations.
diff --git a/src/static/js/ace2_inner.js b/src/static/js/ace2_inner.js
index 129ec7822c5..0bab36695f7 100644
--- a/src/static/js/ace2_inner.js
+++ b/src/static/js/ace2_inner.js
@@ -1474,11 +1474,10 @@ function Ace2Inner(editorInfo, cssManagers) {
   };
 
   const doRepApplyChangeset = (changes, insertsAfterSelection) => {
-    Changeset.unpack(changes).validate();
+    const cs = Changeset.unpack(changes).validate();
 
-    if (Changeset.oldLen(changes) !== rep.alltext.length) {
-      const errMsg = `${Changeset.oldLen(changes)}/${rep.alltext.length}`;
-      throw new Error(`doRepApplyChangeset length mismatch: ${errMsg}`);
+    if (cs.oldLen !== rep.alltext.length) {
+      throw new Error(`doRepApplyChangeset length mismatch: ${cs.oldLen}/${rep.alltext.length}`);
     }
 
     const editEvent = currentCallStack.editEvent;
diff --git a/src/static/js/changesettracker.js b/src/static/js/changesettracker.js
index c01d407b842..8c04c687fd6 100644
--- a/src/static/js/changesettracker.js
+++ b/src/static/js/changesettracker.js
@@ -192,7 +192,7 @@ const makeChangesetTracker = (scheduler, apool, aceCallbacksProvider) => {
       let cs = null;
       if (toSubmit) {
         submittedChangeset = toSubmit;
-        userChangeset = Changeset.identity(Changeset.newLen(toSubmit));
+        userChangeset = Changeset.identity(Changeset.unpack(toSubmit).newLen);
 
         cs = toSubmit;
       }