diff --git a/src/lib/system-info.ts b/src/lib/system-info.ts
index 5ba9fcaa..7a56282f 100644
--- a/src/lib/system-info.ts
+++ b/src/lib/system-info.ts
@@ -69,7 +69,7 @@ export async function getCpuId(): Promise<string | undefined> {
 	try {
 		const buffer = await fs.readFile('/proc/device-tree/serial-number');
 		// Remove the null byte at the end
-		return buffer.toString('utf-8').substr(0, buffer.length - 2);
+		return buffer.toString('utf-8').replace(/\0/g, '');
 	} catch {
 		return undefined;
 	}
diff --git a/test/38-sys-info.spec.ts b/test/38-sys-info.spec.ts
index 54acc432..156b9c22 100644
--- a/test/38-sys-info.spec.ts
+++ b/test/38-sys-info.spec.ts
@@ -119,7 +119,7 @@ describe('System information', async () => {
 				]),
 			);
 			const cpuId = await sysInfo.getCpuId();
-			expect(cpuId).to.equal('1000000001b93f3');
+			expect(cpuId).to.equal('1000000001b93f3f');
 			fsStub.restore();
 		});
 	});