diff --git a/src/browser/Terminal.ts b/src/browser/Terminal.ts
index 24dc7af9..23122f3f 100644
--- a/src/browser/Terminal.ts
+++ b/src/browser/Terminal.ts
@@ -820,7 +820,7 @@ export class Terminal extends CoreTerminal implements ITerminal {
 
       // normal viewport scrolling
       // conditionally stop event, if the viewport still had rows to scroll within
-      if (!this.viewport!.onWheel(ev)) {
+      if (this.viewport!.onWheel(ev)) {
         return this.cancel(ev);
       }
     }, { passive: false }));
diff --git a/src/browser/Viewport.ts b/src/browser/Viewport.ts
index f73594bf..1dfc9e3e 100644
--- a/src/browser/Viewport.ts
+++ b/src/browser/Viewport.ts
@@ -220,7 +220,7 @@ export class Viewport extends Disposable implements IViewport {
 
   private _getPixelsScrolled(ev: WheelEvent): number {
     // Do nothing if it's not a vertical scroll event
-    if (ev.deltaY === 0) {
+    if (ev.deltaY === 0 || ev.shiftKey) {
       return 0;
     }
 
@@ -241,7 +241,7 @@ export class Viewport extends Disposable implements IViewport {
    */
   public getLinesScrolled(ev: WheelEvent): number {
     // Do nothing if it's not a vertical scroll event
-    if (ev.deltaY === 0) {
+    if (ev.deltaY === 0 || ev.shiftKey) {
       return 0;
     }