diff --git a/app/ui.js b/app/ui.js
index 1531cc11..ce20bfc1 100644
--- a/app/ui.js
+++ b/app/ui.js
@@ -30,8 +30,8 @@ window.updateSetting = (name, value) => {
     }
 }
 
-//import "core-js/stable";
-//import "regenerator-runtime/runtime";
+import "core-js/stable";
+import "regenerator-runtime/runtime";
 import * as Log from '../core/util/logging.js';
 import _, { l10n } from './localization.js';
 import { isTouchDevice, isSafari, hasScrollbarGutter, dragThreshold, supportsBinaryClipboard, isFirefox, isWindows, isIOS, supportsPointerLock }
@@ -66,8 +66,6 @@ const UI = {
     controlbarMouseDownClientY: 0,
     controlbarMouseDownOffsetY: 0,
 
-    needToCheckClipboardChange: false,
-
     inhibitReconnect: true,
     reconnectCallback: null,
     reconnectPassword: null,
@@ -462,8 +460,6 @@ const UI = {
             .addEventListener('change', UI.clipboardSend);
         document.getElementById("noVNC_clipboard_clear_button")
             .addEventListener('click', UI.clipboardClear);
-
-        window.addEventListener("focus", UI.copyFromLocalClipboard);
     },
 
     // Add a call to save settings when the element changes,
@@ -1248,16 +1244,6 @@ const UI = {
         }
     },
 
-    readClipboard: function readClipboard(callback) {
-        if (navigator.clipboard && navigator.clipboard.readText) {
-          navigator.clipboard.readText().then(function (text) {
-            return callback(text);
-          }).catch(function () {
-            return Log.Debug("Failed to read system clipboard");
-          });
-        }
-      },
-
     clipboardReceive(e) {
         if (UI.rfb.clipboardDown) {
            var curvalue = document.getElementById('noVNC_clipboard_text').value;
@@ -1291,26 +1277,6 @@ const UI = {
     setTimeout(UI.showOverlay.bind(this, msg, secs), 200);
     },
 
-    copyFromLocalClipboard: function copyFromLocalClipboard() {
-        if (!document.hasFocus()) {
-            Log.Debug("window does not have focus");
-            return;
-        }
-        if (UI.rfb && UI.rfb.clipboardUp && UI.rfb.clipboardSeamless) {
-
-            if (UI.rfb.clipboardBinary) {
-                navigator.clipboard.read().then((data) => {
-                    if (UI.rfb) {
-                        UI.rfb.clipboardPasteDataFrom(data);
-                    }
-                    UI.needToCheckClipboardChange = false;
-                }, (err) => {
-                    Log.Debug("No data in clipboard");
-                }); 
-            }
-        }
-    },
-
     clipboardClear() {
         document.getElementById('noVNC_clipboard_text').value = "";
         UI.rfb.clipboardPasteFrom("");
diff --git a/core/rfb.js b/core/rfb.js
index fa770600..cec38580 100644
--- a/core/rfb.js
+++ b/core/rfb.js
@@ -824,6 +824,27 @@ export default class RFB extends EventTargetMixin {
         this._keyboard.blur();
     }
 
+    checkLocalClipboard() {
+        if (this.clipboardUp && this.clipboardSeamless) {
+
+            if (this.clipboardBinary) {
+                navigator.clipboard.read().then((data) => {
+                    this.clipboardPasteDataFrom(data);
+                }, (err) => {
+                    Log.Debug("No data in clipboard: " + err);
+                }); 
+            } else {
+                if (navigator.clipboard && navigator.clipboard.readText) {
+                    navigator.clipboard.readText().then(function (text) {
+                        this.clipboardPasteFrom(text);
+                    }.bind(this)).catch(function () {
+                      return Log.Debug("Failed to read system clipboard");
+                    });
+                }
+            }
+        }
+    }
+
     clipboardPasteFrom(text) {
         if (this._rfbConnectionState !== 'connected' || this._viewOnly) { return; }
         if (!(typeof text === 'string' && text.length > 0)) { return; }
@@ -1551,6 +1572,7 @@ export default class RFB extends EventTargetMixin {
                     this._keyboard._sendKeyEvent(this._keyboard._keyDownList["MetaRight"], "MetaRight", false);
                     this._keyboard._sendKeyEvent(KeyTable.XK_Control_L, "ControlLeft", true);
                 }
+                this.checkLocalClipboard();
 
                 this._handleMouseButton(pos.x, pos.y,
                                         true, 1 << ev.button);
@@ -2599,7 +2621,10 @@ export default class RFB extends EventTargetMixin {
 
             this.dispatchEvent(new CustomEvent(
                 "clipboard",
-                { detail: { text: text } }));
+                { detail: { text: text } })
+            );
+
+            this._clipHash = 0;
 
         } else {
             //Extended msg.
@@ -3080,15 +3105,15 @@ export default class RFB extends EventTargetMixin {
 
     _sendUdpDowngrade() {
         this._changeTransitConnectionState(this.TransitConnectionStates.Downgrading);
-        const buff = sock._sQ;
-        const offset = sock._sQlen;
+        const buff = this._sock._sQ;
+        const offset = this._sock._sQlen;
 
         buff[offset] = 181; // msg-type
         buff[offset + 1] = 0; // u16 len
         buff[offset + 2] = 0;
 
-        sock._sQlen += 3;
-        sock.flush();
+        this._sock._sQlen += 3;
+        this._sock.flush();
     }
 
     _handleUdpUpgrade() {