As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CLIMB FROM YYZ, 'CABIN ALT' WARNING LIGHT ON DUE TO 'AFT GALLEY DOOR OPEN'. QRH PROCEDURES CARRIED OUT AND AIRCRAFT LANDED BACK TO YYZ. GALLEY DOOR FOUND IMPROPERLY CLOSED BY MAINTENANCE. SEAL CLEANED AND AIRCRAFT PRESSURIZED ON GROUND, NO LEAK FOUND AND NO DOOR WARNING INDICATION. TEST C/OUT IAW MM REF. 21-50-00.