diff --git a/core/rfb.js b/core/rfb.js
index d2075a0d..ea40fd55 100644
--- a/core/rfb.js
+++ b/core/rfb.js
@@ -1117,9 +1117,11 @@ export default class RFB extends EventTargetMixin {
 
         let bmask = RFB._convertButtonMask(ev.buttons);
 
-        let down = ev.type == 'mousedown';
+        let down = false;
         switch (ev.type) {
             case 'mousedown':
+                down = true;
+            // eslint-disable-next-line no-fallthrough
             case 'mouseup':
                 if (this._dragViewport) {
                     this._cursor.setLocalCursor(down ? 'grabbing' : 'grab');