diff --git a/packages/backend-defaults/package.json b/packages/backend-defaults/package.json
index d2bfd7038d..401c507ae2 100644
--- a/packages/backend-defaults/package.json
+++ b/packages/backend-defaults/package.json
@@ -36,6 +36,7 @@
     "@backstage/backend-plugin-api": "workspace:^"
   },
   "devDependencies": {
+    "@backstage/backend-test-utils": "workspace:^",
     "@backstage/cli": "workspace:^"
   },
   "files": [
diff --git a/packages/backend-defaults/src/CreateBackend.test.ts b/packages/backend-defaults/src/CreateBackend.test.ts
index 89a8e96b28..2fa802e0ad 100644
--- a/packages/backend-defaults/src/CreateBackend.test.ts
+++ b/packages/backend-defaults/src/CreateBackend.test.ts
@@ -16,10 +16,17 @@
 
 import {
   coreServices,
+  createBackendPlugin,
   createServiceFactory,
+  createServiceRef,
+  createSharedEnvironment,
 } from '@backstage/backend-plugin-api';
+import { mockConfigFactory } from '@backstage/backend-test-utils';
 import { createBackend } from './CreateBackend';
 
+const fooServiceRef = createServiceRef<string>({ id: 'foo', scope: 'root' });
+const barServiceRef = createServiceRef<string>({ id: 'bar', scope: 'root' });
+
 describe('createBackend', () => {
   it('should not throw when overriding a default service implementation', () => {
     expect(() =>
@@ -69,4 +76,91 @@ describe('createBackend', () => {
       }),
     ).toThrow('The core.pluginMetadata service cannot be overridden');
   });
+
+  it('should throw if an unsupported InternalSharedEnvironment version is passed in', () => {
+    expect(() =>
+      createBackend({
+        env: {} as any,
+      }),
+    ).toThrow(
+      "Shared environment version 'undefined' is invalid or not supported",
+    );
+    expect(() =>
+      createBackend({
+        env: { version: {} } as any,
+      }),
+    ).toThrow(
+      "Shared environment version '[object Object]' is invalid or not supported",
+    );
+    expect(() =>
+      createBackend({
+        env: { version: 'v2' } as any,
+      }),
+    ).toThrow("Shared environment version 'v2' is invalid or not supported");
+  });
+
+  it('should prioritize services correctly', async () => {
+    const backend = createBackend({
+      env: createSharedEnvironment({
+        services: [
+          createServiceFactory({
+            service: coreServices.rootHttpRouter,
+            deps: {},
+            async factory() {
+              return {
+                use() {},
+              };
+            },
+          }),
+          mockConfigFactory({
+            data: { root: 'root-env' },
+          }),
+          createServiceFactory({
+            service: fooServiceRef,
+            deps: {},
+            async factory() {
+              return 'foo-env';
+            },
+          }),
+          createServiceFactory({
+            service: barServiceRef,
+            deps: {},
+            async factory() {
+              return 'bar-env';
+            },
+          }),
+        ],
+      })(),
+      services: [
+        createServiceFactory({
+          service: fooServiceRef,
+          deps: {},
+          factory: async () => 'foo-backend',
+        }),
+      ],
+    });
+
+    expect.assertions(3);
+    backend.add(
+      createBackendPlugin({
+        id: 'test',
+        register(reg) {
+          reg.registerInit({
+            deps: {
+              config: coreServices.config,
+              foo: fooServiceRef,
+              bar: barServiceRef,
+            },
+            async init({ config, foo, bar }) {
+              expect(config.get('root')).toBe('root-env');
+              expect(foo).toBe('foo-backend');
+              expect(bar).toBe('bar-env');
+            },
+          });
+        },
+      })(),
+    );
+
+    await backend.start();
+  });
 });
diff --git a/packages/backend-defaults/src/CreateBackend.ts b/packages/backend-defaults/src/CreateBackend.ts
index 374574645f..e6b5a15336 100644
--- a/packages/backend-defaults/src/CreateBackend.ts
+++ b/packages/backend-defaults/src/CreateBackend.ts
@@ -85,7 +85,9 @@ export function createBackend(options?: CreateBackendOptions): Backend {
   if (options?.env) {
     const env = options.env as unknown as InternalSharedBackendEnvironment;
     if (env.version !== 'v1') {
-      throw new Error(`Unsupported shared environment version: ${env.version}`);
+      throw new Error(
+        `Shared environment version '${env.version}' is invalid or not supported`,
+      );
     }
 
     const environmentServices =
diff --git a/yarn.lock b/yarn.lock
index d6822cad9d..a3c21bddad 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3515,6 +3515,7 @@ __metadata:
   dependencies:
     "@backstage/backend-app-api": "workspace:^"
     "@backstage/backend-plugin-api": "workspace:^"
+    "@backstage/backend-test-utils": "workspace:^"
     "@backstage/cli": "workspace:^"
   languageName: unknown
   linkType: soft