diff --git a/bower.json b/bower.json
index 064b23765..24dac9b55 100644
--- a/bower.json
+++ b/bower.json
@@ -1,6 +1,6 @@
 {
   "name": "pdfjs-dist",
-  "version": "1.0.398",
+  "version": "1.0.400",
   "keywords": [
     "Mozilla",
     "pdf",
diff --git a/build/pdf.combined.js b/build/pdf.combined.js
index 58b6f1926..6551db676 100644
--- a/build/pdf.combined.js
+++ b/build/pdf.combined.js
@@ -21,8 +21,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.0.398';
-PDFJS.build = '7a83291';
+PDFJS.version = '1.0.400';
+PDFJS.build = 'cf4bc42';
 
 (function pdfjsWrapper() {
   // Use strict in our context only - users might not want it
@@ -22311,7 +22311,9 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           };
         }
         return {
-          str: '',
+          // |str| is initially an array which we push individual chars to, and
+          // then runBidi() overwrites it with the final string.
+          str: [],
           dir: null,
           width: 0,
           height: 0,
@@ -22321,7 +22323,8 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       }
 
       function runBidi(textChunk) {
-        var bidiResult = PDFJS.bidi(textChunk.str, -1, textState.font.vertical);
+        var str = textChunk.str.join('');
+        var bidiResult = PDFJS.bidi(str, -1, textState.font.vertical);
         textChunk.str = bidiResult.str;
         textChunk.dir = bidiResult.dir;
         return textChunk;
@@ -22411,7 +22414,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           }
           textState.translateTextMatrix(tx, ty);
 
-          textChunk.str += glyphUnicode;
+          textChunk.str.push(glyphUnicode);
         }
 
         var a = textState.textLineMatrix[0];
@@ -22506,10 +22509,10 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
                     if (fakeSpaces > MULTI_SPACE_FACTOR) {
                       fakeSpaces = Math.round(fakeSpaces);
                       while (fakeSpaces--) {
-                        textChunk.str += ' ';
+                        textChunk.str.push(' ');
                       }
                     } else if (fakeSpaces > SPACE_FACTOR) {
-                      textChunk.str += ' ';
+                      textChunk.str.push(' ');
                     }
                   }
                 }
diff --git a/build/pdf.js b/build/pdf.js
index da1e08a5b..aacbde937 100644
--- a/build/pdf.js
+++ b/build/pdf.js
@@ -21,8 +21,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.0.398';
-PDFJS.build = '7a83291';
+PDFJS.version = '1.0.400';
+PDFJS.build = 'cf4bc42';
 
 (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 2187cb3bd..f17e46365 100644
--- a/build/pdf.worker.js
+++ b/build/pdf.worker.js
@@ -21,8 +21,8 @@ if (typeof PDFJS === 'undefined') {
   (typeof window !== 'undefined' ? window : this).PDFJS = {};
 }
 
-PDFJS.version = '1.0.398';
-PDFJS.build = '7a83291';
+PDFJS.version = '1.0.400';
+PDFJS.build = 'cf4bc42';
 
 (function pdfjsWrapper() {
   // Use strict in our context only - users might not want it
@@ -17475,7 +17475,9 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           };
         }
         return {
-          str: '',
+          // |str| is initially an array which we push individual chars to, and
+          // then runBidi() overwrites it with the final string.
+          str: [],
           dir: null,
           width: 0,
           height: 0,
@@ -17485,7 +17487,8 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       }
 
       function runBidi(textChunk) {
-        var bidiResult = PDFJS.bidi(textChunk.str, -1, textState.font.vertical);
+        var str = textChunk.str.join('');
+        var bidiResult = PDFJS.bidi(str, -1, textState.font.vertical);
         textChunk.str = bidiResult.str;
         textChunk.dir = bidiResult.dir;
         return textChunk;
@@ -17575,7 +17578,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           }
           textState.translateTextMatrix(tx, ty);
 
-          textChunk.str += glyphUnicode;
+          textChunk.str.push(glyphUnicode);
         }
 
         var a = textState.textLineMatrix[0];
@@ -17670,10 +17673,10 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
                     if (fakeSpaces > MULTI_SPACE_FACTOR) {
                       fakeSpaces = Math.round(fakeSpaces);
                       while (fakeSpaces--) {
-                        textChunk.str += ' ';
+                        textChunk.str.push(' ');
                       }
                     } else if (fakeSpaces > SPACE_FACTOR) {
-                      textChunk.str += ' ';
+                      textChunk.str.push(' ');
                     }
                   }
                 }
diff --git a/package.json b/package.json
index 5c850698e..989b3ebc2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pdfjs-dist",
-  "version": "1.0.398",
+  "version": "1.0.400",
   "description": "Generic build of Mozilla's PDF.js library.",
   "keywords": [
     "Mozilla",