diff --git a/gulpfile.js b/gulpfile.js
index 623f6db37..397bea14c 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -122,6 +122,16 @@ function safeSpawnSync(command, parameters, options) {
   return result;
 }
 
+function startNode(args, options) {
+  // Node.js decreased the maximum header size from 80 KB to 8 KB in newer
+  // releases, which is not sufficient for some of our reference test files
+  // (such as `issue6360.pdf`), so we need to restore this value. Note that
+  // this argument needs to be before all other arguments as it needs to be
+  // passed to the Node.js process itself and not to the script that it runs.
+  args.unshift('--max-http-header-size=80000');
+  return spawn('node', args, options);
+}
+
 function createStringSource(filename, content) {
   var source = stream.Readable({ objectMode: true, });
   source._read = function () {
@@ -405,7 +415,7 @@ function createTestSource(testsName, bot) {
       args.push('--strictVerify');
     }
 
-    var testProcess = spawn('node', args, { cwd: TEST_DIR, stdio: 'inherit', });
+    var testProcess = startNode(args, { cwd: TEST_DIR, stdio: 'inherit', });
     testProcess.on('close', function (code) {
       source.push(null);
     });
@@ -435,7 +445,7 @@ function makeRef(done, bot) {
     args.push('--noPrompts', '--strictVerify');
   }
   args.push('--browserManifestFile=' + PDF_BROWSERS);
-  var testProcess = spawn('node', args, { cwd: TEST_DIR, stdio: 'inherit', });
+  var testProcess = startNode(args, { cwd: TEST_DIR, stdio: 'inherit', });
   testProcess.on('close', function (code) {
     done();
   });
@@ -1146,7 +1156,7 @@ gulp.task('baseline', function (done) {
 gulp.task('unittestcli', gulp.series('testing-pre', 'lib', function(done) {
   var options = ['node_modules/jasmine/bin/jasmine',
                  'JASMINE_CONFIG_PATH=test/unit/clitests.json'];
-  var jasmineProcess = spawn('node', options, { stdio: 'inherit', });
+  var jasmineProcess = startNode(options, { stdio: 'inherit', });
   jasmineProcess.on('close', function(code) {
     if (code !== 0) {
       done(new Error('Unit tests failed.'));
@@ -1163,7 +1173,7 @@ gulp.task('lint', gulp.series('default_preferences', function(done) {
   // Ensure that we lint the Firefox specific *.jsm files too.
   var options = ['node_modules/eslint/bin/eslint', '--ext', '.js,.jsm', '.',
                  '--report-unused-disable-directives'];
-  var esLintProcess = spawn('node', options, { stdio: 'inherit', });
+  var esLintProcess = startNode(options, { stdio: 'inherit', });
   esLintProcess.on('close', function (code) {
     if (code !== 0) {
       done(new Error('ESLint failed.'));