diff --git a/libtaskmanager/tasksmodel.cpp b/libtaskmanager/tasksmodel.cpp
--- a/libtaskmanager/tasksmodel.cpp
+++ b/libtaskmanager/tasksmodel.cpp
@@ -552,8 +552,15 @@
                      const QModelIndex &concatProxyIndex = concatProxyModel->index(sortedPreFilterRows.at(i), 0);
 
                      if (appsMatch(concatProxyIndex, idx)) {
-                         sortedPreFilterRows.move(row, i + 1);
-                         moved = true;
+                         // Our sort map contains row indices prior to any filtering, but we don't
+                         // want to sort new tasks in next to siblings we're filtering out higher up
+                         // in the proxy chain, so check in with the filter model.
+                         const QModelIndex &filterProxyIndex = filterProxyModel->mapFromSource(concatProxyIndex);
+
+                         if (filterProxyIndex.isValid()) {
+                            sortedPreFilterRows.move(row, i + 1);
+                            moved = true;
+                         }
 
                          break;
                      }