diff --git a/.publishrc b/.publishrc
index fe0e22548c..be33ddaf32 100644
--- a/.publishrc
+++ b/.publishrc
@@ -8,7 +8,7 @@
     "gitTag": true
   },
   "confirm": false,
-  "publishTag": "latest",
+  "publishTag": "alpha",
   "prePublishScript": "gulp test-server",
   "postPublishScript": "gulp docker-publish"
 }
diff --git a/package.json b/package.json
index da46207e9f..58522c8123 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "testcafe",
   "description": "Automated browser testing for the modern web development stack.",
   "license": "MIT",
-  "version": "1.18.4",
+  "version": "1.18.5-alpha.1",
   "author": {
     "name": "Developer Express Inc.",
     "url": "https://www.devexpress.com/"
diff --git a/src/screenshots/utils.js b/src/screenshots/utils.js
index 5d3fd9f944..abe8d27c5e 100644
--- a/src/screenshots/utils.js
+++ b/src/screenshots/utils.js
@@ -17,7 +17,7 @@ const ALPHABET = '01';
 
 export function generateScreenshotMark () {
     // NOTE: 32-bit id
-    const id = customAlphabet(ALPHABET, MARK_LENGTH);
+    const id = customAlphabet(ALPHABET, MARK_LENGTH)();
 
     // NOTE: array of RGB values
     const markSeed = flatten(map(id, bit => bit === '0' ? [0, 0, 0, 255] : [255, 255, 255, 255]));
diff --git a/test/server/util-test.js b/test/server/util-test.js
index d5897ad246..9d75651be1 100644
--- a/test/server/util-test.js
+++ b/test/server/util-test.js
@@ -22,6 +22,7 @@ const { replaceLeadingSpacesWithNbsp } = require('../../lib/errors/test-run/util
 const createTempProfile                = require('../../lib/browser/provider/built-in/dedicated/chrome/create-temp-profile');
 const parseUserAgent                   = require('../../lib/utils/parse-user-agent');
 const diff                             = require('../../lib/utils/diff');
+const { generateScreenshotMark }       = require('../../lib/screenshots/utils');
 
 const {
     buildChromeArgs,
@@ -605,4 +606,13 @@ describe('Utils', () => {
             expect(preferences.profile.content_settings.exceptions.popups).to.be.undefined;
         });
     });
+
+    it('generateScreenshotMark', () => {
+        const { markSeed } = generateScreenshotMark();
+
+        expect(markSeed.length).eql(128);
+
+        for (const markPixel of markSeed)
+            expect(markPixel === 0 || markPixel === 255).is.true;
+    });
 });