diff --git a/server/src/controllers/controllerUtils.ts b/server/src/controllers/controllerUtils.ts
index 67dc71a70..0e765bae8 100755
--- a/server/src/controllers/controllerUtils.ts
+++ b/server/src/controllers/controllerUtils.ts
@@ -6,7 +6,8 @@ type SSLCheckerType = typeof sslChecker;
 export const fetchMonitorCertificate = async (checker: SSLCheckerType, monitor: Monitor): Promise<SSLDetails> => {
 	const monitorUrl = new URL(monitor.url);
 	const hostname = monitorUrl.hostname;
-	const cert = await checker(hostname);
+	const port = monitorUrl.port ? Number(monitorUrl.port) : undefined;
+	const cert = await checker(hostname, port ? { port } : undefined);
 	if (cert?.validTo === null || cert?.validTo === undefined) {
 		throw new Error("Certificate not found");
 	}
diff --git a/server/test/unit/controllers/controllerUtils.test.ts b/server/test/unit/controllers/controllerUtils.test.ts
new file mode 100644
index 000000000..c3ac92246
--- /dev/null
+++ b/server/test/unit/controllers/controllerUtils.test.ts
@@ -0,0 +1,34 @@
+import { describe, expect, it, jest } from "@jest/globals";
+import { fetchMonitorCertificate } from "../../../src/controllers/controllerUtils.ts";
+import type { Monitor } from "../../../src/types/monitor.ts";
+
+const certificate = {
+	daysRemaining: 30,
+	valid: true,
+	validFrom: "2026-01-01T00:00:00.000Z",
+	validTo: "2026-02-01T00:00:00.000Z",
+	validFor: ["checkmate.example.org"],
+};
+
+const makeMonitor = (url: string) =>
+	({
+		url,
+	}) as Monitor;
+
+describe("fetchMonitorCertificate", () => {
+	it("passes a custom HTTPS port to the SSL checker", async () => {
+		const checker = jest.fn().mockResolvedValue(certificate);
+
+		await fetchMonitorCertificate(checker, makeMonitor("https://checkmate.example.org:54321/status"));
+
+		expect(checker).toHaveBeenCalledWith("checkmate.example.org", { port: 54321 });
+	});
+
+	it("uses the SSL checker's default port when the URL does not include one", async () => {
+		const checker = jest.fn().mockResolvedValue(certificate);
+
+		await fetchMonitorCertificate(checker, makeMonitor("https://checkmate.example.org/status"));
+
+		expect(checker).toHaveBeenCalledWith("checkmate.example.org", undefined);
+	});
+});