diff --git a/libtaskmanager/tasksmodel.cpp b/libtaskmanager/tasksmodel.cpp
--- a/libtaskmanager/tasksmodel.cpp
+++ b/libtaskmanager/tasksmodel.cpp
@@ -631,6 +631,10 @@
         delete flattenGroupsProxyModel;
         flattenGroupsProxyModel = nullptr;
 
+        // filterAcceptsRow filters out group parents in inline grouping
+        // mode, and setSourceModel surprisingly doesn't invalidate.
+        q->invalidateFilter();
+
         if (sortMode == SortManual) {
             forceResort();
         }