diff --git a/backend/routers/auth.py b/backend/routers/auth.py
index 166d48d..4c7215b 100644
--- a/backend/routers/auth.py
+++ b/backend/routers/auth.py
@@ -235,18 +235,17 @@ async def register(req: RegisterRequest, request: Request):
         verification_token = secrets.token_urlsafe(32)
         verification_expires = datetime.now(timezone.utc) + timedelta(hours=24)
 
-        # Create profile (inactive until verified)
-        profile_id = str(secrets.token_hex(16))
+        # Create profile (inactive until verified) — profiles.id ist SERIAL (INT), keine String-IDs einfügen.
         pin_hash = hash_pin(password)
         trial_ends = datetime.now(timezone.utc) + timedelta(days=14)  # 14-day trial
 
         cur.execute("""
             INSERT INTO profiles (
-                id, name, email, pin_hash, auth_type, role, tier,
+                name, email, pin_hash, auth_type, role, tier,
                 email_verified, verification_token, verification_expires,
                 trial_ends_at, created_at
-            ) VALUES (%s, %s, %s, %s, 'email', 'trainer', 'free', FALSE, %s, %s, %s, CURRENT_TIMESTAMP)
-        """, (profile_id, name, email, pin_hash, verification_token, verification_expires, trial_ends))
+            ) VALUES (%s, %s, %s, 'email', 'trainer', 'free', FALSE, %s, %s, %s, CURRENT_TIMESTAMP)
+        """, (name, email, pin_hash, verification_token, verification_expires, trial_ends))
 
     # Send verification email
     app_url = os.getenv("APP_URL", "https://mitai.jinkendo.de")