diff --git a/core/rfb.js b/core/rfb.js
index e6647eff..0dbebe7d 100644
--- a/core/rfb.js
+++ b/core/rfb.js
@@ -287,6 +287,7 @@ export default class RFB extends EventTargetMixin {
         this._viewOnly = false;
         this._clipViewport = false;
         this._scaleViewport = false;
+        this._customScale = null;
         this._resizeSession = false;
 
         this._showDotCursor = false;
@@ -326,8 +327,19 @@ export default class RFB extends EventTargetMixin {
         this._updateClip();
     }
 
+    get customScale() { return this._customScale; }
+    set customScale(level) {
+        this._customScale = level;
+        if (level) {
+            this.scaleViewport = false;
+        }
+    }
+
     get scaleViewport() { return this._scaleViewport; }
     set scaleViewport(scale) {
+        if (scale) {
+            this.customScale = null;
+        }
         this._scaleViewport = scale;
         // Scaling trumps clipping, so we may need to adjust
         // clipping when enabling or disabling scaling
@@ -742,7 +754,7 @@ export default class RFB extends EventTargetMixin {
 
     _updateScale() {
         if (!this._scaleViewport) {
-            this._display.scale = 1.0;
+            this._display.scale = this._customScale || 1.0;
         } else {
             const size = this._screenSize();
             this._display.autoscale(size.w, size.h);
diff --git a/tests/test.rfb.js b/tests/test.rfb.js
index 75d1e118..b0dc5ab2 100644
--- a/tests/test.rfb.js
+++ b/tests/test.rfb.js
@@ -741,6 +741,21 @@ describe('Remote Frame Buffer Protocol Client', function () {
             expect(spy.set).to.have.been.calledWith(false);
         });
 
+        it('should update the custom scale setting when changing the property', function () {
+            client.customScale = 1.5;
+
+            const spy = sinon.spy(client, "customScale", ["set"]);
+
+            client.scaleViewport = false;
+            expect(spy.set).to.not.have.been.called;
+
+            spy.set.resetHistory();
+
+            client.scaleViewport = true;
+            expect(spy.set).to.have.been.calledOnce;
+            expect(spy.set).to.have.been.calledWith(null);
+        });
+
         it('should update the scaling when the container size changes', function () {
             sinon.spy(client._display, "autoscale");
 
@@ -787,6 +802,34 @@ describe('Remote Frame Buffer Protocol Client', function () {
         });
     });
 
+    describe('Custom Scale', function () {
+        let client;
+        beforeEach(function () {
+            client = makeRFB();
+            container.style.width = '70px';
+            container.style.height = '80px';
+            client.scaleViewport = true;
+        });
+
+        it('should update display scale factor when setting the property', function () {
+            const spy = sinon.spy(client._display, "scale", ["set"]);
+            sinon.spy(client._display, "autoscale");
+
+            client.customScale = 1.5;
+            expect(spy.set).to.have.been.calledOnce;
+            expect(spy.set).to.have.been.calledWith(1.5);
+            expect(client._display.autoscale).to.not.have.been.called;
+        });
+
+        it('should not update display scale factor when nullifying the property', function () {
+            const spy = sinon.spy(client._display, "scale", ["set"]);
+
+            client.customScale = null;
+            expect(spy.set).to.not.have.been.called;
+        });
+
+    });
+
     describe('Remote resize', function () {
         let client;
         beforeEach(function () {