diff --git a/Sources/Kanna/CSS.swift b/Sources/Kanna/CSS.swift
index 7fc5c81..9f7e9f8 100755
--- a/Sources/Kanna/CSS.swift
+++ b/Sources/Kanna/CSS.swift
@@ -103,10 +103,14 @@ public enum CSS {
     }
 }
 
+private var regexDict: [String: AKRegularExpression] = [:]
 private func firstMatch(_ pattern: String) -> (String) -> AKTextCheckingResult? {
     return { str in
         let length = str.utf16.count
-        guard let regex = try? AKRegularExpression(pattern: pattern, options: .caseInsensitive) else {
+        if regexDict[pattern] == nil {
+            regexDict[pattern] = try? AKRegularExpression(pattern: pattern, options: .caseInsensitive)
+        }
+        guard let regex = regexDict[pattern] else {
             return nil
         }
         if let result = regex.firstMatch(in: str, options: .reportProgress, range: NSRange(location: 0, length: length)) {
diff --git a/Tests/KannaTests/KannaCSSTests.swift b/Tests/KannaTests/KannaCSSTests.swift
index 01c6e9a..1e11893 100644
--- a/Tests/KannaTests/KannaCSSTests.swift
+++ b/Tests/KannaTests/KannaCSSTests.swift
@@ -93,12 +93,16 @@ class KannaCSSTests: XCTestCase {
     ]
 
     func testCSStoXPath() {
-        for testCase in css2xpath {
-            do {
-                let xpath = try CSS.toXPath(testCase.css)
-                XCTAssert(xpath == testCase.xpath, "Create XPath = [\(xpath)] != [\(testCase.xpath)]")
-            } catch {
-                XCTAssert(false, error.localizedDescription)
+        self.measure {
+            (0..<100).forEach { _ in
+            for testCase in css2xpath {
+                do {
+                    let xpath = try CSS.toXPath(testCase.css)
+                    XCTAssert(xpath == testCase.xpath, "Create XPath = [\(xpath)] != [\(testCase.xpath)]")
+                } catch {
+                    XCTAssert(false, error.localizedDescription)
+                }
+            }
             }
         }