diff --git a/packages/client/ui-theme/tests/elevation-styles.client.spec.ts b/packages/client/ui-theme/tests/elevation-styles.client.spec.ts
index ade17f1f06..01d704a723 100644
--- a/packages/client/ui-theme/tests/elevation-styles.client.spec.ts
+++ b/packages/client/ui-theme/tests/elevation-styles.client.spec.ts
@@ -113,7 +113,7 @@ describe('translucent menu surfaces pair fill and filter', () => {
     ] as const
     const files = packageStylesheets()
     for (const [suffix, container, background] of surfaces) {
-      const file = files.find(candidate => candidate.replaceAll('\\', '/').endsWith(suffix))
+      const file = files.find(candidate => candidate.endsWith(suffix))
       expect(file, suffix).toBeDefined()
       const rules = parseRules(readFileSync(file!, 'utf8'))
       const declarations = (selector: string) => new Map(rules
diff --git a/packages/client/ui-theme/tests/stylesheet-scan.ts b/packages/client/ui-theme/tests/stylesheet-scan.ts
index d91e308889..c658a21254 100644
--- a/packages/client/ui-theme/tests/stylesheet-scan.ts
+++ b/packages/client/ui-theme/tests/stylesheet-scan.ts
@@ -74,7 +74,8 @@ export function varReferences(value: string): string[] {
 /**
  * Every CSS file shipped as package source, excluding build output and
  * installed dependencies.
- * @returns absolute paths of the stylesheets under packages/.
+ * @returns absolute stylesheet paths under packages/, `/`-separated on every
+ *   platform so specs can match repo-relative suffixes verbatim.
  */
 export function packageStylesheets(): string[] {
   const found: string[] = []
@@ -83,7 +84,7 @@ export function packageStylesheets(): string[] {
       const path = join(dir, entry.name)
       if (entry.isDirectory()) {
         if (entry.name !== 'node_modules' && entry.name !== 'lib' && entry.name !== 'dist') walk(path)
-      } else if (entry.name.endsWith('.css')) found.push(path)
+      } else if (entry.name.endsWith('.css')) found.push(path.replaceAll('\\', '/'))
     }
   }
   walk(PACKAGES_DIR)