diff --git a/Packages/viewerbase/lib/helpers/isDisplaySetActive.js b/Packages/viewerbase/lib/helpers/isDisplaySetActive.js
index 251e0ecc6..36bca06da 100644
--- a/Packages/viewerbase/lib/helpers/isDisplaySetActive.js
+++ b/Packages/viewerbase/lib/helpers/isDisplaySetActive.js
@@ -10,19 +10,40 @@ Template.registerHelper('isDisplaySetActive', (displaySetInstanceUid, viewportIn
         return;
     }
 
-    let viewportData;
-    if (_.isUndefined(viewportIndex)) {
-        viewportData = layoutManager.viewportData;
-    } else {
-        viewportData = [layoutManager.viewportData[viewportIndex]];
-    }
-
+    // Check if the display set is current visible in any of the layout
+    // manager's displayed viewports. Note that we have to check the 
+    // onscreen number of viewports here, since the layout manager will
+    // keep the viewport data of old viewports, even after the layout is changed.
+    //
+    // This behaviour is intentional. If the user displays four viewports, then assigns
+    // display sets to them, and then switches to / from another layout configuration,
+    // we don't want them to lose their specified viewports.
     let result = false;
-    _.each(viewportData, data => {
+    if (_.isUndefined(viewportIndex)) {
+        // Get the number of viewports that are currently displayed
+        // (Note, viewportData may have more entries!)
+        const currentNumberOfViewports = layoutManager.getNumberOfViewports();
+
+        // Loop through the viewport data up until the currently displayed
+        // number of viewports
+        let viewportData = layoutManager.viewportData;
+        for (let i = 0; i < currentNumberOfViewports; i++) {
+            const data = viewportData[i];
+
+            // If the display set is displayed in this viewport, stop here
+            if (data && data.displaySetInstanceUid === displaySetInstanceUid) {
+                result = true;
+                break;
+            }
+        }
+    } else {
+        const data = layoutManager.viewportData[viewportIndex];
+
+        // If the display set is displayed in this viewport, stop here
         if (data && data.displaySetInstanceUid === displaySetInstanceUid) {
             result = true;
         }
-    });
+    }
 
     return result;
 });