diff --git a/src/core/chunked_stream.js b/src/core/chunked_stream.js
index cf0e6b700..5eeb3f082 100644
--- a/src/core/chunked_stream.js
+++ b/src/core/chunked_stream.js
@@ -155,8 +155,15 @@ var ChunkedStream = (function ChunkedStreamClosure() {
       if (pos >= this.end) {
         return -1;
       }
-      this.ensureByte(pos);
-      return this.bytes[this.pos++];
+      var byte = this.bytes[pos];
+      if (byte === 0) {
+        // |byte| might be zero, because the corresponding chunk has not been
+        // loaded yet. In this case, this.ensureByte(pos) will throw an
+        // exception and nothing is returned.
+        this.ensureByte(pos);
+      }
+      this.pos++;
+      return byte;
     },
 
     getUint16: function ChunkedStream_getUint16() {
diff --git a/src/core/core.js b/src/core/core.js
index e3a821028..f012b271c 100644
--- a/src/core/core.js
+++ b/src/core/core.js
@@ -14,8 +14,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* globals assert, calculateMD5, Catalog, Dict, error, info, isArray,
-           isArrayBuffer, isName, isStream, isString, createPromiseCapability,
+/* globals assert, bytesToString, calculateMD5, Catalog, Dict, error, info,
+           isArray, isArrayBuffer, isName, isStream, isString,
            Linearization, NullStream, PartialEvaluator, shadow, Stream, Lexer,
            StreamsSequenceStream, stringToPDFString, stringToBytes, Util, XRef,
            MissingDataException, Promise, Annotation, ObjectLoader, OperatorList
@@ -301,14 +301,10 @@ var PDFDocument = (function PDFDocumentClosure() {
   function find(stream, needle, limit, backwards) {
     var pos = stream.pos;
     var end = stream.end;
-    var strBuf = [];
     if (pos + limit > end) {
       limit = end - pos;
     }
-    for (var n = 0; n < limit; ++n) {
-      strBuf.push(String.fromCharCode(stream.getByte()));
-    }
-    var str = strBuf.join('');
+    var str = bytesToString(stream.getBytes(limit));
     stream.pos = pos;
     var index = backwards ? str.lastIndexOf(needle) : str.indexOf(needle);
     if (index == -1) {
diff --git a/src/core/stream.js b/src/core/stream.js
index e8afcc822..1d49fbb05 100644
--- a/src/core/stream.js
+++ b/src/core/stream.js
@@ -531,12 +531,10 @@ var FlateStream = (function FlateStreamClosure() {
           this.eof = true;
         }
       } else {
-        for (var n = bufferLength; n < end; ++n) {
-          if ((b = str.getByte()) === -1) {
-            this.eof = true;
-            break;
-          }
-          buffer[n] = b;
+        var block = str.getBytes(blockLen);
+        buffer.set(block, bufferLength);
+        if (block.length < blockLen) {
+          this.eof = true;
         }
       }
       return;