diff --git a/web/apps/photos/src/components/Sidebar/SubscriptionCard.tsx b/web/apps/photos/src/components/Sidebar/SubscriptionCard.tsx
index d812e839dd..6db0b94e09 100644
--- a/web/apps/photos/src/components/Sidebar/SubscriptionCard.tsx
+++ b/web/apps/photos/src/components/Sidebar/SubscriptionCard.tsx
@@ -111,7 +111,7 @@ const IndividualSubscriptionCardContent: React.FC<
     IndividualSubscriptionCardContentProps
 > = ({ userDetails }) => {
     const totalStorage =
-        userDetails.subscription.storage + (userDetails.storageBonus ?? 0);
+        userDetails.subscription.storage + userDetails.storageBonus;
     return (
         <>
             <StorageSection storage={totalStorage} usage={userDetails.usage} />
@@ -230,7 +230,7 @@ const FamilySubscriptionCardContent: React.FC<
         }
     }, [userDetails]);
     const totalStorage =
-        userDetails.familyData.storage + (userDetails.storageBonus ?? 0);
+        userDetails.familyData.storage + userDetails.storageBonus;
 
     return (
         <>
diff --git a/web/apps/photos/src/components/pages/gallery/PlanSelector.tsx b/web/apps/photos/src/components/pages/gallery/PlanSelector.tsx
index 2bbae10bfb..bf6c011ca7 100644
--- a/web/apps/photos/src/components/pages/gallery/PlanSelector.tsx
+++ b/web/apps/photos/src/components/pages/gallery/PlanSelector.tsx
@@ -105,8 +105,8 @@ const PlanSelectorCard: React.FC<PlanSelectorCardProps> = ({
     const userDetails = useUserDetailsSnapshot();
 
     const [plansData, setPlansData] = useState<PlansData | undefined>();
-    const [planPeriod, setPlanPeriod] = useState<PlanPeriod>(
-        userDetails?.subscription?.period || "month",
+    const [planPeriod, setPlanPeriod] = useState<PlanPeriod | undefined>(
+        userDetails?.subscription?.period,
     );
 
     const usage = userDetails ? planUsage(userDetails) : 0;
@@ -443,9 +443,7 @@ function PaidSubscriptionPlanSelectorCard({
 
 function PeriodToggler({ planPeriod, togglePeriod }) {
     const handleChange = (_, newPlanPeriod: PlanPeriod) => {
-        if (newPlanPeriod !== null && newPlanPeriod !== planPeriod) {
-            togglePeriod();
-        }
+        if (newPlanPeriod !== planPeriod) togglePeriod();
     };
 
     return (
diff --git a/web/packages/new/photos/services/plan.ts b/web/packages/new/photos/services/plan.ts
index a091f13bb2..e7bb52418a 100644
--- a/web/packages/new/photos/services/plan.ts
+++ b/web/packages/new/photos/services/plan.ts
@@ -10,28 +10,40 @@ import { z } from "zod";
 import type { UserDetails } from "./user";
 import { syncUserDetails, userDetailsSnapshot } from "./user";
 
-const PlanPeriod = z.enum(["month", "year"]);
-
 /**
  * Validity of the plan.
  */
-export type PlanPeriod = z.infer<typeof PlanPeriod>;
+export type PlanPeriod = "month" | "year";
 
 export const Subscription = z.object({
+    /**
+     * Store-specific ID of the product ("plan") that the user has subscribed
+     * to. e.g. if the user has subscribed to a plan using Stripe, then this
+     * will be the stripeID of the corresponding {@link Plan}.
+     *
+     * For free plans, the productID will be the constant "free".
+     */
     productID: z.string(),
+    /**
+     * Storage (in bytes) that the user can use.
+     */
     storage: z.number(),
+    /**
+     * Epoch microseconds indicating the time until which the user's
+     * subscription is valid.
+     */
     expiryTime: z.number(),
     paymentProvider: z.string(),
+    price: z.string(),
+    period: z
+        .string()
+        .transform((p) => (p == "month" || p == "year" ? p : undefined)),
     attributes: z
         .object({
             isCancelled: z.boolean().nullish().transform(nullToUndefined),
         })
         .nullish()
         .transform(nullToUndefined),
-    price: z.string(),
-    // TODO: We get back subscriptions without a period on cancel / reactivate.
-    // Handle them better, or remove this TODO.
-    period: z.enum(["month", "year", ""]).transform((s) => (s ? s : "month")),
 });
 
 /**
@@ -121,7 +133,9 @@ const Plan = z.object({
     stripeID: z.string().nullish().transform(nullToUndefined),
     storage: z.number(),
     price: z.string(),
-    period: PlanPeriod,
+    period: z
+        .string()
+        .transform((p) => (p == "month" || p == "year" ? p : undefined)),
 });
 
 /**
@@ -131,7 +145,7 @@ export type Plan = z.infer<typeof Plan>;
 
 const PlansData = z.object({
     freePlan: z.object({
-        /* Number of bytes available in the free plan */
+        /* Number of bytes available in the free plan. */
         storage: z.number(),
     }),
     plans: z.array(Plan),
@@ -399,9 +413,8 @@ export const hasExceededStorageQuota = (userDetails: UserDetails) => {
         storage = userDetails.familyData?.storage ?? 0;
     } else {
         usage = userDetails.usage;
-        storage = userDetails.subscription?.storage ?? 0;
+        storage = userDetails.subscription.storage;
     }
 
-    const bonusStorage = userDetails.storageBonus ?? 0;
-    return usage > storage + bonusStorage;
+    return usage > storage + userDetails.storageBonus;
 };
diff --git a/web/packages/new/photos/services/user.ts b/web/packages/new/photos/services/user.ts
index e842f443eb..551f09f599 100644
--- a/web/packages/new/photos/services/user.ts
+++ b/web/packages/new/photos/services/user.ts
@@ -1,9 +1,10 @@
 import { authenticatedRequestHeaders, ensureOk } from "@/base/http";
 import { getKV, setKV } from "@/base/kv";
 import { apiURL } from "@/base/origins";
+import { nullishToZero, nullToUndefined } from "@/utils/transform";
 import { getData, LS_KEYS, setLSUser } from "@ente/shared/storage/localStorage";
 import { z } from "zod";
-import { FamilyData, Subscription, BonusData } from "./plan";
+import { BonusData, FamilyData, Subscription } from "./plan";
 
 /**
  * Zod schema for {@link UserDetails}
@@ -11,11 +12,11 @@ import { FamilyData, Subscription, BonusData } from "./plan";
 const UserDetails = z.object({
     email: z.string(),
     usage: z.number(),
-    fileCount: z.number().optional(),
+    fileCount: z.number().nullish().transform(nullishToZero),
     subscription: Subscription,
-    familyData: FamilyData.optional(),
-    storageBonus: z.number().optional(),
-    bonusData: BonusData.optional(),
+    familyData: FamilyData.nullish().transform(nullToUndefined),
+    storageBonus: z.number().nullish().transform(nullishToZero),
+    bonusData: BonusData.nullish().transform(nullToUndefined),
 });
 
 export type UserDetails = z.infer<typeof UserDetails>;
diff --git a/web/packages/utils/transform.ts b/web/packages/utils/transform.ts
index 0d400619a4..16e1c1c4e0 100644
--- a/web/packages/utils/transform.ts
+++ b/web/packages/utils/transform.ts
@@ -1,3 +1,10 @@
-/** Convert `null` to `undefined`, passthrough everything else unchanged. */
+/**
+ * Convert `null` to `undefined`, passthrough everything else unchanged.
+ */
 export const nullToUndefined = <T>(v: T | null | undefined): T | undefined =>
     v === null ? undefined : v;
+
+/**
+ * Convert `null` and `undefined` to `0`, passthrough everything else unchanged.
+ */
+export const nullishToZero = (v: number | null | undefined) => v ?? 0;