diff --git a/glimmer-scoped-css/src/ast-transform.ts b/glimmer-scoped-css/src/ast-transform.ts
index b724d6d..58db130 100644
--- a/glimmer-scoped-css/src/ast-transform.ts
+++ b/glimmer-scoped-css/src/ast-transform.ts
@@ -83,7 +83,19 @@ export function generateScopedCSSPlugin(
               `./${basename(env.filename)}.${encodedCss}.glimmer-scoped.css`
             );
 
-            return null;
+            // Return an empty <style> stub so Glimmer still has something to remove during teardown.
+            // Without this stub, the runtime-inserted <style> lives in <head> and Ember will throw
+            // when it later tries to remove the original node. The stub also carries the unique
+            // scoped attribute value so the runtime script can detect which stylesheet to update.
+            node.attributes = [
+              builders.attr(
+                'data-boxel-scoped-css-stub',
+                builders.text(dataAttribute)
+              ),
+            ];
+            node.children = [];
+
+            return node;
           } else {
             if (node.tag.startsWith(':')) {
               return node;
diff --git a/test-app/package.json b/test-app/package.json
index f8198ee..16181db 100644
--- a/test-app/package.json
+++ b/test-app/package.json
@@ -17,7 +17,9 @@
     "lint:js": "eslint . --cache",
     "lint:js:fix": "eslint . --fix",
     "lint:types": "tsc --noEmit",
+    "prestart": "pnpm --dir ../test-addon-to-import build",
     "start": "ember serve",
+    "pretest": "pnpm --dir ../test-addon-to-import build",
     "test": "concurrently \"npm:lint\" \"npm:test:*\" --names \"lint,test:\"",
     "test:ember": "ember test"
   },
diff --git a/test-app/tests/acceptance/scoped-css-test.ts b/test-app/tests/acceptance/scoped-css-test.ts
index 3cf041f..7d0d12f 100644
--- a/test-app/tests/acceptance/scoped-css-test.ts
+++ b/test-app/tests/acceptance/scoped-css-test.ts
@@ -88,7 +88,7 @@ module('Acceptance | scoped css', function (hooks) {
 
     const multipleInnerElement = find('[data-test-multiple-inner]');
     const multipleInnerElementBeforeStyle = getComputedStyle(
-      multipleInnerElement!,
+      multipleInnerElement as Element,
       ':before'
     );
 
@@ -130,19 +130,45 @@ module('Acceptance | scoped css', function (hooks) {
   test('an addon can use scoped styles', async function (assert) {
     await visit('/');
 
-    assert.dom('[data-scoped-underline-addon-component]').hasStyle({
-      textDecoration: 'underline solid rgb(0, 0, 0)',
-    });
+    const underlineComponent = find('[data-scoped-underline-addon-component]');
+    if (!underlineComponent) {
+      throw new Error(
+        '[data-scoped-underline-addon-component] element not found'
+      );
+    }
+    const underlineComponentStyles = getComputedStyle(underlineComponent);
+    assert.strictEqual(
+      underlineComponentStyles.textDecorationLine,
+      'underline'
+    );
+    assert.strictEqual(
+      underlineComponentStyles.textDecorationColor,
+      'rgb(0, 0, 0)'
+    );
 
     assert
       .dom('[data-test-underline-component-outside-addon]')
       .doesNotHaveStyle({
-        textDecoration: 'underline solid rgb(0, 0, 0)',
+        textDecoration: 'underline rgb(0, 0, 0)',
       });
 
-    assert.dom('[data-test-paragraph-with-class-styled-by-addon]').hasStyle({
-      textDecoration: 'underline solid rgb(0, 0, 0)',
-    });
+    const classStyledParagraph = find(
+      '[data-test-paragraph-with-class-styled-by-addon]'
+    );
+    if (!classStyledParagraph) {
+      throw new Error(
+        '[data-test-paragraph-with-class-styled-by-addon] element not found'
+      );
+    }
+    const classStyledParagraphStyles = getComputedStyle(classStyledParagraph);
+    assert.strictEqual(
+      classStyledParagraphStyles.textDecorationLine,
+      'underline'
+    );
+    assert.strictEqual(
+      classStyledParagraphStyles.textDecorationColor,
+      'rgb(0, 0, 0)'
+    );
   });
 
   test('unscoped styles can use interpolation', async function (assert) {
