diff --git a/autotests/integration/activities_test.cpp b/autotests/integration/activities_test.cpp
--- a/autotests/integration/activities_test.cpp
+++ b/autotests/integration/activities_test.cpp
@@ -125,15 +125,19 @@
     QCOMPARE(client->window(), w);
     QVERIFY(client->isDecorated());
 
+    //verify the test machine doesn't have the following activities used
     QVERIFY(!Activities::self()->all().contains(QStringLiteral("foo")));
     QVERIFY(!Activities::self()->all().contains(QStringLiteral("bar")));
+
+    //setting the client to an invalid activities should result in the client being on all activities
+    client->setOnActivity(QStringLiteral("foo"), true);
+    QVERIFY(client->isOnAllActivities());
+    QVERIFY(!client->activities().contains(QLatin1String("foo")));
+
     client->setOnActivities(QStringList{QStringLiteral("foo"), QStringLiteral("bar")});
-    QEXPECT_FAIL("", "D1982", Continue);
     QVERIFY(client->isOnAllActivities());
-    QEXPECT_FAIL("", "D1982", Continue);
-    QVERIFY(!client->isOnActivity(QStringLiteral("foo")));
-    QEXPECT_FAIL("", "D1982", Continue);
-    QVERIFY(!client->isOnActivity(QStringLiteral("bar")));
+    QVERIFY(!client->activities().contains(QLatin1String("foo")));
+    QVERIFY(!client->activities().contains(QLatin1String("bar")));
 
     // and destroy the window again
     xcb_unmap_window(c.data(), w);
diff --git a/client.cpp b/client.cpp
--- a/client.cpp
+++ b/client.cpp
@@ -1240,6 +1240,16 @@
     newActivitiesList = joinedActivitiesList.split(u',', QString::SkipEmptyParts);
 
     QStringList allActivities = Activities::self()->all();
+
+    auto it = newActivitiesList.begin();
+    while (it != newActivitiesList.end()) {
+        if (! allActivities.contains(*it)) {
+            it = newActivitiesList.erase(it);
+        } else {
+            it++;
+        }
+    }
+
     if (// If we got the request to be on all activities explicitly
         newActivitiesList.isEmpty() || joinedActivitiesList == Activities::nullUuid() ||
         // If we got a list of activities that covers all activities