             let parseError = ReadabilityError.unableToParseScriptResult(rawResult: result as? String)
             
             guard let resultData = (result as? String)?.data(using: .utf8) else {
-                self?.completionHandler(nil, webView, error)
+                self?.completionHandler(nil, webView, error, self?.previousNavigationDelegate)
                 return
             }
             guard let jsonResultOptional = try? JSONSerialization.jsonObject(with: resultData, options: []), let jsonResult = jsonResultOptional as? [String: String?], let contentOptional = jsonResult["content"], let content = contentOptional, let titleOptional = jsonResult["title"], let bylineOptional = jsonResult["byline"] else {
-                self?.completionHandler(nil, webView, parseError)
+                self?.completionHandler(nil, webView, parseError, self?.previousNavigationDelegate)
                 return
             }
             guard let html = self?.renderHTML(

public class Readability: NSObject, WKNavigationDelegate, WKScriptMessageHandler {
    private weak var webView: WKWebView?
    private let ownWebView: WKWebView?
    private let completionHandler: ((_ content: String?, _ rawWebView: WKWebView, _ error: Error?) -> Void)
    private let readabilityUserScript = ReadabilityUserScript(scriptInjectionTime: .atDocumentEnd)
    private var isRenderingReadabilityHTML = false
    private let conversionTime: ReadabilityConversionTime

        addContentRules(completion: contentRulesAddedCallback)
        
        webView?.configuration.suppressesIncrementalRendering = true
        
        previousNavigationDelegate = webView?.navigationDelegate
        webView?.navigationDelegate = self
        
        webView?.configuration.userContentController.removeScriptMessageHandler(forName: "readabilityJavascriptLoaded")
        webView?.configuration.userContentController.add(self, name: "readabilityJavascriptLoaded")
        webView?.addObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress), options: .new, context: nil)
