diff --git a/applets/taskmanager/package/contents/ui/Task.qml b/applets/taskmanager/package/contents/ui/Task.qml
--- a/applets/taskmanager/package/contents/ui/Task.qml
+++ b/applets/taskmanager/package/contents/ui/Task.qml
@@ -227,7 +227,7 @@
                     subTextEntries.push(i18n("On %1", task.DesktopName));
                 }
 
-                if (task.OnAllActivities) {
+                if (task.OnAllActivities && backend.numberOfActivities() > 1) {
                     subTextEntries.push(i18nc("Which virtual desktop a window is currently on",
                         "Available on all activities"));
                 } else if (plasmoid.configuration.showOnlyCurrentActivity) {
diff --git a/applets/taskmanager/plugin/backend.h b/applets/taskmanager/plugin/backend.h
--- a/applets/taskmanager/plugin/backend.h
+++ b/applets/taskmanager/plugin/backend.h
@@ -34,6 +34,10 @@
     class LauncherItem;
 }
 
+namespace KActivities {
+    class Consumer;
+}
+
 class Backend : public QObject
 {
     Q_OBJECT
@@ -86,6 +90,7 @@
 
         Q_INVOKABLE bool canPresentWindows() const;
         Q_INVOKABLE int numberOfDesktops() const;
+        Q_INVOKABLE int numberOfActivities() const;
 
     public Q_SLOTS:
         void activateItem(int id, bool toggle);
@@ -129,6 +134,7 @@
         bool m_highlightWindows;
         QList<WId> m_windowsToHighlight;
         QString m_launchers;
+        KActivities::Consumer *m_activitiesConsumer;
 };
 
 #endif
diff --git a/applets/taskmanager/plugin/backend.cpp b/applets/taskmanager/plugin/backend.cpp
--- a/applets/taskmanager/plugin/backend.cpp
+++ b/applets/taskmanager/plugin/backend.cpp
@@ -42,6 +42,7 @@
 #include <KService>
 #include <kwindoweffects.h>
 
+#include <KActivities/Consumer>
 #include <KActivitiesExperimentalStats/Cleaning>
 #include <KActivitiesExperimentalStats/ResultSet>
 #include <KActivitiesExperimentalStats/Terms>
@@ -58,7 +59,8 @@
     m_taskManagerItem(0),
     m_toolTipItem(0),
     m_panelWinId(0),
-    m_highlightWindows(false)
+    m_highlightWindows(false),
+    m_activitiesConsumer(new KActivities::Consumer(this))
 {
     connect(m_groupManager, SIGNAL(launcherListChanged()), this, SLOT(updateLaunchersCache()));
 }
@@ -628,6 +630,11 @@
     return KWindowSystem::numberOfDesktops();
 }
 
+int Backend::numberOfActivities() const
+{
+    return m_activitiesConsumer->activities(KActivities::Info::State::Running).count();
+}
+
 void Backend::presentWindows(int groupParentId)
 {
     TaskManager::AbstractGroupableItem *item = m_groupManager->rootGroup()->getMemberById(groupParentId);