diff --git a/src/display/display_utils.js b/src/display/display_utils.js
index 92e87536214893..6c981e0ca8e793 100644
--- a/src/display/display_utils.js
+++ b/src/display/display_utils.js
@@ -486,5 +486,6 @@ export {
   DOMSVGFactory,
   StatTimer,
   DummyStatTimer,
+  isValidFetchUrl,
   loadScript,
 };
diff --git a/src/pdf.js b/src/pdf.js
index 10c463df72659e..bd024d99264d80 100644
--- a/src/pdf.js
+++ b/src/pdf.js
@@ -38,14 +38,17 @@ if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
     pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
       return new PDFNodeStream(params);
     });
-  } else if (isFetchSupported()) {
-    let PDFFetchStream = require('./display/fetch_stream.js').PDFFetchStream;
-    pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
-      return new PDFFetchStream(params);
-    });
   } else {
     let PDFNetworkStream = require('./display/network.js').PDFNetworkStream;
+    let PDFFetchStream;
+    if (isFetchSupported()) {
+      PDFFetchStream = require('./display/fetch_stream.js').PDFFetchStream;
+    }
     pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
+      if (PDFFetchStream &&
+          pdfjsDisplayDisplayUtils.isValidFetchUrl(params.url)) {
+        return new PDFFetchStream(params);
+      }
       return new PDFNetworkStream(params);
     });
   }
@@ -70,8 +73,8 @@ if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
     PDFFetchStream = require('./display/fetch_stream.js').PDFFetchStream;
   }
   pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
-    if (PDFFetchStream && /^https?:/i.test(params.url)) {
-      // "fetch" is only supported for http(s), not file/ftp.
+    if (PDFFetchStream &&
+        pdfjsDisplayDisplayUtils.isValidFetchUrl(params.url)) {
       return new PDFFetchStream(params);
     }
     return new PDFNetworkStream(params);
diff --git a/test/unit/display_utils_spec.js b/test/unit/display_utils_spec.js
index 474cefe8e4e932..67f339fa713d94 100644
--- a/test/unit/display_utils_spec.js
+++ b/test/unit/display_utils_spec.js
@@ -14,7 +14,7 @@
  */
 
 import {
-  DOMSVGFactory, getFilenameFromUrl
+  DOMSVGFactory, getFilenameFromUrl, isValidFetchUrl
 } from '../../src/display/display_utils';
 import isNodeJS from '../../src/shared/is_node';
 
@@ -94,4 +94,28 @@ describe('display_utils', function() {
       expect(result).toEqual(expected);
     });
   });
+
+  describe('isValidFetchUrl', function() {
+    it('handles invalid Fetch URLs', function() {
+      expect(isValidFetchUrl(null)).toEqual(false);
+      expect(isValidFetchUrl(100)).toEqual(false);
+      expect(isValidFetchUrl('foo')).toEqual(false);
+      expect(isValidFetchUrl('/foo', 100)).toEqual(false);
+    });
+
+    it('handles relative Fetch URLs', function() {
+      expect(isValidFetchUrl('/foo', 'file://www.example.com')).toEqual(false);
+      expect(isValidFetchUrl('/foo', 'http://www.example.com')).toEqual(true);
+    });
+
+    it('handles unsupported Fetch protocols', function() {
+      expect(isValidFetchUrl('file://www.example.com')).toEqual(false);
+      expect(isValidFetchUrl('ftp://www.example.com')).toEqual(false);
+    });
+
+    it('handles supported Fetch protocols', function() {
+      expect(isValidFetchUrl('http://www.example.com')).toEqual(true);
+      expect(isValidFetchUrl('https://www.example.com')).toEqual(true);
+    });
+  });
 });