diff --git a/src/display/api.js b/src/display/api.js
index 5a37e574c..029c3ac59 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -1885,6 +1885,7 @@ var WorkerTransport = (function WorkerTransportClosure() {
               isEvalSupported: params.isEvalSupported,
               disableFontFace: params.disableFontFace,
               ignoreErrors: params.ignoreErrors,
+              onUnsupportedFeature: this._onUnsupportedFeature.bind(this),
               fontRegistry,
             });
             var fontReady = (fontObjs) => {
@@ -1987,15 +1988,7 @@ var WorkerTransport = (function WorkerTransportClosure() {
         }
       }, this);
 
-      messageHandler.on('UnsupportedFeature', function(data) {
-        if (this.destroyed) {
-          return; // Ignore any pending requests if the worker was terminated.
-        }
-        let loadingTask = this.loadingTask;
-        if (loadingTask.onUnsupportedFeature) {
-          loadingTask.onUnsupportedFeature(data.featureId);
-        }
-      }, this);
+      messageHandler.on('UnsupportedFeature', this._onUnsupportedFeature, this);
 
       messageHandler.on('JpegDecode', function(data) {
         if (this.destroyed) {
@@ -2061,6 +2054,16 @@ var WorkerTransport = (function WorkerTransportClosure() {
       }, this);
     },
 
+    _onUnsupportedFeature({ featureId, }) {
+      if (this.destroyed) {
+        return; // Ignore any pending requests if the worker was terminated.
+      }
+      let loadingTask = this.loadingTask;
+      if (loadingTask.onUnsupportedFeature) {
+        loadingTask.onUnsupportedFeature(featureId);
+      }
+    },
+
     getData: function WorkerTransport_getData() {
       return this.messageHandler.sendWithPromise('GetData', null);
     },
diff --git a/src/display/font_loader.js b/src/display/font_loader.js
index be662bcae..cb7b26f49 100644
--- a/src/display/font_loader.js
+++ b/src/display/font_loader.js
@@ -14,7 +14,8 @@
  */
 
 import {
-  assert, bytesToString, isEvalSupported, shadow, string32, warn
+  assert, bytesToString, isEvalSupported, shadow, string32,
+  UNSUPPORTED_FEATURES, warn
 } from '../shared/util';
 
 function FontLoader(docId) {
@@ -339,6 +340,7 @@ var FontFaceObject = (function FontFaceObjectClosure() {
   function FontFaceObject(translatedData, { isEvalSupported = true,
                                             disableFontFace = false,
                                             ignoreErrors = false,
+                                            onUnsupportedFeature = null,
                                             fontRegistry = null, }) {
     this.compiledGlyphs = Object.create(null);
     // importing translated data
@@ -348,6 +350,7 @@ var FontFaceObject = (function FontFaceObjectClosure() {
     this.isEvalSupported = isEvalSupported !== false;
     this.disableFontFace = disableFontFace === true;
     this.ignoreErrors = ignoreErrors === true;
+    this._onUnsupportedFeature = onUnsupportedFeature;
     this.fontRegistry = fontRegistry;
   }
   FontFaceObject.prototype = {
@@ -399,6 +402,9 @@ var FontFaceObject = (function FontFaceObjectClosure() {
         if (!this.ignoreErrors) {
           throw ex;
         }
+        if (this._onUnsupportedFeature) {
+          this._onUnsupportedFeature({ featureId: UNSUPPORTED_FEATURES.font, });
+        }
         warn(`getPathGenerator - ignoring character: "${ex}".`);
 
         return this.compiledGlyphs[character] = function(c, size) {