diff --git a/kioslave/pop3/pop3.cpp b/kioslave/pop3/pop3.cpp
--- a/kioslave/pop3/pop3.cpp
+++ b/kioslave/pop3/pop3.cpp
@@ -41,8 +41,14 @@
 #include <QCryptographicHash>
 #include <QNetworkProxy>
 
+#include <kio_version.h>
+#if KIO_VERSION >= QT_VERSION_CHECK(5, 65, 0)
+#include <QSslSocket>
+#else
+#include <KTcpSocket>
+#endif
+
 #include <kio/slaveinterface.h>
-#include <ktcpsocket.h>
 
 #define GREETING_BUF_LEN 1024
 #define MAX_RESPONSE_LEN 512
@@ -622,7 +628,11 @@
         || metaData(QStringLiteral("useProxy")) != QLatin1String("on")) {
         qCDebug(POP3_LOG) << "requested to use no proxy";
 
+#if KIO_VERSION >= QT_VERSION_CHECK(5, 65, 0)
+        QSslSocket *sock = qobject_cast<QSslSocket *>(socket());
+#else
         KTcpSocket *sock = qobject_cast<KTcpSocket *>(socket());
+#endif
         if (sock) {
             QNetworkProxy proxy;
             proxy.setType(QNetworkProxy::NoProxy);
diff --git a/resources/pop3/autotests/fakeserver/fakeserver.h b/resources/pop3/autotests/fakeserver/fakeserver.h
--- a/resources/pop3/autotests/fakeserver/fakeserver.h
+++ b/resources/pop3/autotests/fakeserver/fakeserver.h
@@ -75,8 +75,8 @@
 
     // We use one big mutex to protect everything
     // There shouldn't be deadlocks, as there are only 2 places where the functions
-    // are called: From the KTcpSocket signals, which are triggered by the POP3 ioslave,
-    //             and from the actual test.
+    // are called: From the KTcpSocket (or QSslSocket with KIO >= 5.65) signals, which
+    // are triggered by the POP3 ioslave, and from the actual test.
     mutable QMutex mMutex;
 };