diff --git a/bower.json b/bower.json
index 0a3dc8b49..72c40f4d7 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "pdfjs-dist",
-  "version": "1.1.18",
+  "version": "1.1.20",
   "main": [
     "build/pdf.js",
     "build/pdf.worker.js"
diff --git a/build/pdf.combined.js b/build/pdf.combined.js
index 81d89ae96..7464bdd6c 100644
--- a/build/pdf.combined.js
+++ b/build/pdf.combined.js
@@ -22,8 +22,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.1.18';
-PDFJS.build = '64d49e1';
+PDFJS.version = '1.1.20';
+PDFJS.build = '3a8d4a7';
 
 (function pdfjsWrapper() {
   // Use strict in our context only - users might not want it
@@ -18201,8 +18201,11 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       var cmap, cmapObj = toUnicode;
       if (isName(cmapObj)) {
         cmap = CMapFactory.create(cmapObj,
-          { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null).getMap();
-        return new ToUnicodeMap(cmap);
+          { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null);
+        if (cmap instanceof IdentityCMap) {
+          return new IdentityToUnicodeMap(0, 0xFFFF);
+        }
+        return new ToUnicodeMap(cmap.getMap());
       } else if (isStream(cmapObj)) {
         cmap = CMapFactory.create(cmapObj,
           { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null).getMap();
@@ -22657,7 +22660,7 @@ var IdentityToUnicodeMap = (function IdentityToUnicodeMapClosure() {
 
   IdentityToUnicodeMap.prototype = {
     get length() {
-      error('should not access .length');
+      return (this.lastChar + 1) - this.firstChar;
     },
 
     forEach: function (callback) {
diff --git a/build/pdf.js b/build/pdf.js
index 052b14d74..e32877972 100644
--- a/build/pdf.js
+++ b/build/pdf.js
@@ -22,8 +22,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.1.18';
-PDFJS.build = '64d49e1';
+PDFJS.version = '1.1.20';
+PDFJS.build = '3a8d4a7';
 
 (function pdfjsWrapper() {
   // Use strict in our context only - users might not want it
diff --git a/build/pdf.worker.js b/build/pdf.worker.js
index 06e8d5ffa..efac40b69 100644
--- a/build/pdf.worker.js
+++ b/build/pdf.worker.js
@@ -22,8 +22,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.1.18';
-PDFJS.build = '64d49e1';
+PDFJS.version = '1.1.20';
+PDFJS.build = '3a8d4a7';
 
 (function pdfjsWrapper() {
   // Use strict in our context only - users might not want it
@@ -11853,8 +11853,11 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       var cmap, cmapObj = toUnicode;
       if (isName(cmapObj)) {
         cmap = CMapFactory.create(cmapObj,
-          { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null).getMap();
-        return new ToUnicodeMap(cmap);
+          { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null);
+        if (cmap instanceof IdentityCMap) {
+          return new IdentityToUnicodeMap(0, 0xFFFF);
+        }
+        return new ToUnicodeMap(cmap.getMap());
       } else if (isStream(cmapObj)) {
         cmap = CMapFactory.create(cmapObj,
           { url: PDFJS.cMapUrl, packed: PDFJS.cMapPacked }, null).getMap();
@@ -16309,7 +16312,7 @@ var IdentityToUnicodeMap = (function IdentityToUnicodeMapClosure() {
 
   IdentityToUnicodeMap.prototype = {
     get length() {
-      error('should not access .length');
+      return (this.lastChar + 1) - this.firstChar;
     },
 
     forEach: function (callback) {
diff --git a/package.json b/package.json
index 257374806..c09e66e19 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pdfjs-dist",
-  "version": "1.1.18",
+  "version": "1.1.20",
   "description": "Generic build of Mozilla's PDF.js library.",
   "keywords": [
     "Mozilla",