diff --git a/src/components/sections/ContactSection.tsx b/src/components/sections/ContactSection.tsx
index 2756617..ac14373 100644
--- a/src/components/sections/ContactSection.tsx
+++ b/src/components/sections/ContactSection.tsx
@@ -101,8 +101,8 @@ export function ContactSection() {
                 {error("email")}
               </div>
               <div>
-                <label className="field-label" htmlFor="ct-phone">Telefon (optional)</label>
-                <input {...fieldProps("phone")} className="field" type="tel" autoComplete="tel" maxLength={60} />
+                <label className="field-label" htmlFor="ct-phone">Telefon</label>
+                <input {...fieldProps("phone")} className="field" type="tel" autoComplete="tel" required maxLength={40} />
                 {error("phone")}
               </div>
               <div>
diff --git a/src/lib/contact.ts b/src/lib/contact.ts
index 23bc4a6..16ecd02 100644
--- a/src/lib/contact.ts
+++ b/src/lib/contact.ts
@@ -28,7 +28,13 @@ const optionalText = (max: number) =>
 export const contactRequestSchema = z.object({
   name: z.string().trim().min(2, "Bitte gib deinen Namen an.").max(120),
   email: z.string().trim().max(200).pipe(z.email("Bitte gib eine gültige E-Mail-Adresse an.")),
-  phone: optionalText(60),
+  // Gleiche Regel wie bei der Buchung.
+  phone: z
+    .string("Bitte gib eine Telefonnummer an.")
+    .trim()
+    .min(6, "Bitte gib eine Telefonnummer an.")
+    .max(40)
+    .regex(/^[+0-9 ()/-]+$/, "Die Telefonnummer darf nur Ziffern, Leerzeichen und + ( ) / - enthalten."),
   availability: optionalText(200),
   message: optionalText(2000),
   privacy: z.literal(true, { error: "Bitte bestätige die Datenschutzhinweise." }),
diff --git a/tests/contact.integration.test.ts b/tests/contact.integration.test.ts
index 48ec55c..221b348 100644
--- a/tests/contact.integration.test.ts
+++ b/tests/contact.integration.test.ts
@@ -10,7 +10,7 @@ function request(overrides: Record<string, unknown> = {}) {
   return contactRequestSchema.parse({
     name: "Lena Beispiel",
     email: "lena@example.org",
-    phone: "",
+    phone: "+49 170 1234567",
     availability: "abends",
     message: "Passt das Camp für Einsteigerinnen?",
     privacy: true,
@@ -61,6 +61,10 @@ describe("Erstgespräch", () => {
   test("Pflichtangaben und Einwilligung werden serverseitig geprüft", () => {
     expect(contactRequestSchema.safeParse({ name: "L", email: "kein-mail", privacy: false }).success).toBe(false);
     expect(contactRequestSchema.safeParse({ name: "Lena", email: "lena@example.org", privacy: false }).success).toBe(false);
-    expect(request({ phone: "  " }).phone).toBeNull();
+    const base = { name: "Lena", email: "lena@example.org", privacy: true };
+    expect(contactRequestSchema.safeParse(base).success).toBe(false);
+    expect(contactRequestSchema.safeParse({ ...base, phone: "  " }).success).toBe(false);
+    expect(contactRequestSchema.safeParse({ ...base, phone: "abc123456" }).success).toBe(false);
+    expect(request({ phone: " +49 170 1234567 " }).phone).toBe("+49 170 1234567");
   });
 });