diff --git a/.github/workflows/store-delivery.yml b/.github/workflows/store-delivery.yml
index 5f07b0fd..55255911 100644
--- a/.github/workflows/store-delivery.yml
+++ b/.github/workflows/store-delivery.yml
@@ -352,10 +352,13 @@ jobs:
           };
           write("notes_en", join(summary.changes?.["en-US"]));
           write("notes_zh", join(summary.changes?.["zh-CN"]));
-          write(
-            "notes_ja",
-            join(summary.changes?.ja || summary.changes?.["ja-JP"]),
-          );
+          const notesJa = join(summary.changes?.ja || summary.changes?.["ja-JP"]);
+          if (!notesJa) {
+            throw new Error(
+              "release-summary.json is missing Japanese What's New (ja or ja-JP). Pass --change-locale ja:...",
+            );
+          }
+          write("notes_ja", notesJa);
           NODE
 
       - name: Set up Ruby and fastlane
diff --git a/apps/ios/fastlane/Fastfile b/apps/ios/fastlane/Fastfile
index 5833050c..1f120613 100644
--- a/apps/ios/fastlane/Fastfile
+++ b/apps/ios/fastlane/Fastfile
@@ -11,8 +11,14 @@ platform :ios do
     notes_en = ENV["APP_STORE_RELEASE_NOTES_EN"].to_s.strip
     has_notes = notes_zh != "" && notes_en != ""
     release_notes = has_notes ? { "zh-Hans" => notes_zh, "en-US" => notes_en } : nil
-    if has_notes && ENV["APP_STORE_RELEASE_NOTES_JA"].to_s.strip != ""
-      release_notes["ja"] = ENV.fetch("APP_STORE_RELEASE_NOTES_JA")
+    if has_notes
+      notes_ja = ENV["APP_STORE_RELEASE_NOTES_JA"].to_s.strip
+      if notes_ja == ""
+        UI.user_error!(
+          "APP_STORE_RELEASE_NOTES_JA is required because the App Store listing includes Japanese What's New.",
+        )
+      end
+      release_notes["ja"] = notes_ja
     end
 
     api_key = app_store_connect_api_key(
diff --git a/scripts/store-delivery.test.mjs b/scripts/store-delivery.test.mjs
index de0cb72d..c00ee522 100644
--- a/scripts/store-delivery.test.mjs
+++ b/scripts/store-delivery.test.mjs
@@ -86,6 +86,7 @@ describe("store delivery command", () => {
       "APP_STORE_BUILD_NUMBER: ${{ steps.ios_build.outputs.build_number }}",
     );
     expect(workflow).toContain("APP_STORE_RELEASE_NOTES_EN:");
+    expect(workflow).toContain("missing Japanese What's New");
     expect(workflow).not.toContain(
       "Pass ios_build_number; do not build from apps/mobile or EAS.",
     );
@@ -111,6 +112,7 @@ describe("store delivery command", () => {
       "utf8",
     );
     expect(fastfile).toContain("precheck_include_in_app_purchases: false");
+    expect(fastfile).toContain("APP_STORE_RELEASE_NOTES_JA is required");
   });
 
   test("replaces the GitHub APK with the Play-signed universal APK", () => {