diff --git a/src/core/chunked_stream.js b/src/core/chunked_stream.js
index 26a93f673..39c1cb677 100644
--- a/src/core/chunked_stream.js
+++ b/src/core/chunked_stream.js
@@ -218,6 +218,12 @@ class ChunkedStream {
   }
 
   getByteRange(begin, end) {
+    if (begin < 0) {
+      begin = 0;
+    }
+    if (end > this.end) {
+      end = this.end;
+    }
     this.ensureRange(begin, end);
     return this.bytes.subarray(begin, end);
   }
diff --git a/src/core/document.js b/src/core/document.js
index 05cc27374..73b14e9a9 100644
--- a/src/core/document.js
+++ b/src/core/document.js
@@ -598,20 +598,16 @@ class PDFDocument {
         idArray[0] !== EMPTY_FINGERPRINT) {
       hash = stringToBytes(idArray[0]);
     } else {
-      if (this.stream.ensureRange) {
-        this.stream.ensureRange(0,
-          Math.min(FINGERPRINT_FIRST_BYTES, this.stream.end));
-      }
-      hash = calculateMD5(this.stream.bytes.subarray(0,
-        FINGERPRINT_FIRST_BYTES), 0, FINGERPRINT_FIRST_BYTES);
+      hash = calculateMD5(this.stream.getByteRange(0, FINGERPRINT_FIRST_BYTES),
+                          0, FINGERPRINT_FIRST_BYTES);
     }
 
-    let fingerprint = '';
+    const fingerprintBuf = [];
     for (let i = 0, ii = hash.length; i < ii; i++) {
       const hex = hash[i].toString(16);
-      fingerprint += (hex.length === 1 ? '0' + hex : hex);
+      fingerprintBuf.push(hex.padStart(2, '0'));
     }
-    return shadow(this, 'fingerprint', fingerprint);
+    return shadow(this, 'fingerprint', fingerprintBuf.join(''));
   }
 
   _getLinearizationPage(pageIndex) {
diff --git a/src/core/stream.js b/src/core/stream.js
index ae57f9023..1867c8c99 100644
--- a/src/core/stream.js
+++ b/src/core/stream.js
@@ -19,7 +19,9 @@
  * license.
  */
 
-import { FormatError, isSpace, stringToBytes } from '../shared/util';
+import {
+  FormatError, isSpace, stringToBytes, unreachable
+} from '../shared/util';
 import { isDict } from './primitives';
 
 var Stream = (function StreamClosure() {
@@ -92,6 +94,17 @@ var Stream = (function StreamClosure() {
       this.pos -= bytes.length;
       return bytes;
     },
+
+    getByteRange(begin, end) {
+      if (begin < 0) {
+        begin = 0;
+      }
+      if (end > this.end) {
+        end = this.end;
+      }
+      return this.bytes.subarray(begin, end);
+    },
+
     skip: function Stream_skip(n) {
       if (!n) {
         n = 1;
@@ -236,6 +249,11 @@ var DecodeStream = (function DecodeStreamClosure() {
       }
       return new Stream(this.buffer, start, length, dict);
     },
+
+    getByteRange(begin, end) {
+      unreachable('Should not call DecodeStream.getByteRange');
+    },
+
     skip: function DecodeStream_skip(n) {
       if (!n) {
         n = 1;
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 10325b9f3..b32014e08 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -413,9 +413,7 @@ describe('api', function() {
       expect(doc.numPages).toEqual(3);
     });
     it('gets fingerprint', function() {
-      var fingerprint = doc.fingerprint;
-      expect(typeof fingerprint).toEqual('string');
-      expect(fingerprint.length > 0).toEqual(true);
+      expect(doc.fingerprint).toEqual('ea8b35919d6279a369e835bde778611b');
     });
     it('gets page', function(done) {
       var promise = doc.getPage(1);
@@ -934,23 +932,22 @@ describe('api', function() {
     });
 
     it('checks that fingerprints are unique', function(done) {
-      var loadingTask1 = getDocument(buildGetDocumentParams('issue4436r.pdf'));
+      const loadingTask1 = getDocument(
+        buildGetDocumentParams('issue4436r.pdf'));
+      const loadingTask2 = getDocument(buildGetDocumentParams('issue4575.pdf'));
 
-      var loadingTask2 = getDocument(buildGetDocumentParams('issue4575.pdf'));
-
-      var promises = [loadingTask1.promise,
-                      loadingTask2.promise];
-      Promise.all(promises).then(function (data) {
-        var fingerprint1 = data[0].fingerprint;
-        expect(typeof fingerprint1).toEqual('string');
-        expect(fingerprint1.length > 0).toEqual(true);
-
-        var fingerprint2 = data[1].fingerprint;
-        expect(typeof fingerprint2).toEqual('string');
-        expect(fingerprint2.length > 0).toEqual(true);
+      Promise.all([
+        loadingTask1.promise,
+        loadingTask2.promise
+      ]).then(function(data) {
+        const fingerprint1 = data[0].fingerprint;
+        const fingerprint2 = data[1].fingerprint;
 
         expect(fingerprint1).not.toEqual(fingerprint2);
 
+        expect(fingerprint1).toEqual('2f695a83d6e7553c24fc08b7ac69712d');
+        expect(fingerprint2).toEqual('04c7126b34a46b6d4d6e7a1eff7edcb6');
+
         Promise.all([
           loadingTask1.destroy(),
           loadingTask2.destroy()