diff --git a/packages/core/src/utils/countable-set.ts b/packages/core/src/utils/countable-set.ts
index 7eab83c0b3..6b7e144b7a 100644
--- a/packages/core/src/utils/countable-set.ts
+++ b/packages/core/src/utils/countable-set.ts
@@ -4,8 +4,6 @@ export class CountableSet<K> extends Set<K> {
   constructor(values?: Iterable<K>) {
     super(values)
     this._map ??= new Map()
-    for (const value of values ?? [])
-      this.add(value)
   }
 
   add(key: K) {
diff --git a/test/countable-set.test.ts b/test/countable-set.test.ts
new file mode 100644
index 0000000000..83571182ba
--- /dev/null
+++ b/test/countable-set.test.ts
@@ -0,0 +1,74 @@
+import { describe, expect, test } from 'vitest'
+import { CountableSet } from '../packages/unocss'
+
+describe('CountableSet', () => {
+  test('constructor', () => {
+    const s = new CountableSet(['bar1', 'bar2', 'bar3', 'bar2'])
+
+    expect(s).toMatchInlineSnapshot(`
+      Set {
+        "bar1",
+        "bar2",
+        "bar3",
+      }
+    `)
+
+    expect(s._map).toMatchInlineSnapshot(`
+      Map {
+        "bar1" => 1,
+        "bar2" => 2,
+        "bar3" => 1,
+      }
+    `)
+  })
+
+  test('add', () => {
+    const s = new CountableSet()
+
+    s.add('bar1')
+    s.add('bar2')
+    s.add('bar2')
+
+    expect(s).toMatchInlineSnapshot(`
+      Set {
+        "bar1",
+        "bar2",
+      }
+    `)
+
+    expect(s._map).toMatchInlineSnapshot(`
+      Map {
+        "bar1" => 1,
+        "bar2" => 2,
+      }
+    `)
+  })
+
+  test('getCount', () => {
+    const s = new CountableSet(['bar1', 'bar2', 'bar2'])
+
+    expect(s.getCount('bar1')).toBe(1)
+    expect(s.getCount('bar2')).toBe(2)
+  })
+
+  test('setCount', () => {
+    const s = new CountableSet()
+
+    s.setCount('bar1', 2)
+    s.setCount('bar2', 1)
+
+    expect(s).toMatchInlineSnapshot(`
+      Set {
+        "bar1",
+        "bar2",
+      }
+    `)
+
+    expect(s._map).toMatchInlineSnapshot(`
+      Map {
+        "bar1" => 2,
+        "bar2" => 1,
+      }
+    `)
+  })
+})