angular
diff --git a/‎packages/platform-server/src/server.ts
Lines changed: 7 additions & 4 deletions b/‎packages/platform-server/src/server.ts
Lines changed: 7 additions & 4 deletions
diff --git a/‎packages/platform-server/test/hydration_utils.ts
Lines changed: 21 additions & 13 deletions b/‎packages/platform-server/test/hydration_utils.ts
Lines changed: 21 additions & 13 deletions
@@ -116,7 +116,8 @@ function _document(injector: Injector) {
  * @publicApi
  */
 export function platformServer(extraProviders?: StaticProvider[] | undefined): PlatformRef {
-  if (typeof ngServerMode === 'undefined') {
+  const noServerModeSet = typeof ngServerMode === 'undefined';
+  if (noServerModeSet) {
     globalThis['ngServerMode'] = true;
   }
 
@@ -126,9 +127,11 @@ export function platformServer(extraProviders?: StaticProvider[] | undefined): P
     INTERNAL_SERVER_PLATFORM_PROVIDERS,
   )(extraProviders);
 
-  platform.onDestroy(() => {
-    globalThis['ngServerMode'] = undefined;
-  });
+  if (noServerModeSet) {
+    platform.onDestroy(() => {
+      globalThis['ngServerMode'] = undefined;
+    });
+  }
 
   return platform;
 }
@@ -253,19 +253,27 @@ export async function ssr(
     enableHydration?: boolean;
   } = {},
 ): Promise<string> {
-  const defaultHtml = DEFAULT_DOCUMENT;
-  const {enableHydration = true, envProviders = [], hydrationFeatures = () => []} = options;
-  const providers = [
-    ...envProviders,
-    provideServerRendering(),
-    enableHydration ? provideClientHydration(...hydrationFeatures()) : [],
-  ];
-
-  const bootstrap = () => bootstrapApplication(component, {providers});
-
-  return renderApplication(bootstrap, {
-    document: options?.doc ?? defaultHtml,
-  });
+  try {
+    // Enter server mode for the duration of this function.
+    globalThis['ngServerMode'] = true;
+
+    const defaultHtml = DEFAULT_DOCUMENT;
+    const {enableHydration = true, envProviders = [], hydrationFeatures = () => []} = options;
+    const providers = [
+      ...envProviders,
+      provideServerRendering(),
+      enableHydration ? provideClientHydration(...hydrationFeatures()) : [],
+    ];
+
+    const bootstrap = () => bootstrapApplication(component, {providers});
+
+    return await renderApplication(bootstrap, {
+      document: options?.doc ?? defaultHtml,
+    });
+  } finally {
+    // Leave server mode so the remaining test is back in "client mode".
+    globalThis['ngServerMode'] = undefined;
+  }
 }
 
 /**