diff --git a/javascript/src/utilities/signingUtilities.js b/javascript/src/utilities/signingUtilities.js
index 2fa2064cb262f70771a965f419cfc7e51ede8c19..338c627008502fbe3caca72f966d1e15a4596df8 100644
--- a/javascript/src/utilities/signingUtilities.js
+++ b/javascript/src/utilities/signingUtilities.js
@@ -222,6 +222,7 @@ function createCertificate(certData, issuerData = null) {
     const serialNumberBuffer = new ArrayBuffer(20);
     const serialNumberView = new Uint8Array(serialNumberBuffer);
     pkijs.getRandomValues(serialNumberView);
+    serialNumberView[0] &= 0x7f;
     // noinspection JSUnresolvedFunction
     certificate.serialNumber = new asn1js.Integer({
       valueHex: serialNumberView