diff --git a/packaging/build/after-pack.cjs b/packaging/build/after-pack.cjs
index 170731252..869b04c35 100644
--- a/packaging/build/after-pack.cjs
+++ b/packaging/build/after-pack.cjs
@@ -30,6 +30,20 @@ function copyPluginSdk(resourcesDir, sdkDir = path.join(repoRoot, "packages", "p
 
 exports.copyPluginSdk = copyPluginSdk;
 
+/** Mac App Store builds report "mas", not "darwin", but are still .app bundles. */
+function resourcesDirFor({ electronPlatformName, appOutDir, packager }) {
+  return ["darwin", "mas"].includes(electronPlatformName)
+    ? path.join(
+        appOutDir,
+        `${packager.appInfo.productFilename}.app`,
+        "Contents",
+        "Resources",
+      )
+    : path.join(appOutDir, "resources");
+}
+
+exports.resourcesDirFor = resourcesDirFor;
+
 exports.default = async function afterPack(context) {
   const { targets, appOutDir } = context;
 
@@ -39,15 +53,7 @@ exports.default = async function afterPack(context) {
     fs.writeFileSync(markerPath, "");
   }
 
-  const resourcesDir =
-    context.electronPlatformName === "darwin"
-      ? path.join(
-          appOutDir,
-          `${context.packager.appInfo.productFilename}.app`,
-          "Contents",
-          "Resources",
-        )
-      : path.join(appOutDir, "resources");
+  const resourcesDir = resourcesDirFor(context);
 
   copyPluginSdk(resourcesDir);
 
diff --git a/src/backend/tests/electron/after-pack.test.ts b/src/backend/tests/electron/after-pack.test.ts
index 450bad0d7..bceb44609 100644
--- a/src/backend/tests/electron/after-pack.test.ts
+++ b/src/backend/tests/electron/after-pack.test.ts
@@ -5,9 +5,14 @@ import path from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
 
 const require = createRequire(import.meta.url);
-const { copyPluginSdk } =
+const { copyPluginSdk, resourcesDirFor } =
   require("../../../../packaging/build/after-pack.cjs") as {
     copyPluginSdk: (resourcesDir: string, sdkDir?: string) => string;
+    resourcesDirFor: (context: {
+      electronPlatformName: string;
+      appOutDir: string;
+      packager: { appInfo: { productFilename: string } };
+    }) => string;
   };
 
 let dir: string;
@@ -53,4 +58,30 @@ describe("afterPack plugin SDK copy", () => {
       "npm run build:sdk",
     );
   });
+
+  it.each(["darwin", "mas"])(
+    "copies into the app bundle for %s builds",
+    (electronPlatformName) => {
+      const context = {
+        electronPlatformName,
+        appOutDir: "/out",
+        packager: { appInfo: { productFilename: "Termix" } },
+      };
+      expect(resourcesDirFor(context)).toBe(
+        path.join("/out", "Termix.app", "Contents", "Resources"),
+      );
+    },
+  );
+
+  it.each(["win32", "linux"])(
+    "copies into resources for %s builds",
+    (electronPlatformName) => {
+      const context = {
+        electronPlatformName,
+        appOutDir: "/out",
+        packager: { appInfo: { productFilename: "Termix" } },
+      };
+      expect(resourcesDirFor(context)).toBe(path.join("/out", "resources"));
+    },
+  );
 });