diff --git a/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyDiscoveryManager.cs b/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyDiscoveryManager.cs
index bb8d1ac0f2..fec2072275 100644
--- a/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyDiscoveryManager.cs
+++ b/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyDiscoveryManager.cs
@@ -99,7 +99,17 @@ public void DiscoverTests(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEve
         // marked as NotDiscovered.
         _dataAggregator.MarkSourcesWithStatus(discoveryCriteria.Sources, DiscoveryStatus.NotDiscovered);
 
-        _parallelOperationManager.StartWork(workloads, eventHandler, GetParallelEventHandler, InitializeDiscoverTestsOnConcurrentManager, DiscoverTestsOnConcurrentManager);
+        if (nonRunnableWorkloads.Count > 0)
+        {
+            // We found some sources that don't associate to any runtime provider and so they cannot run.
+            // Mark the sources as skipped.
+
+            _dataAggregator.MarkSourcesWithStatus(nonRunnableWorkloads.SelectMany(w => w.Work.Sources), DiscoveryStatus.SkippedDiscovery);
+            // TODO: in strict mode keep them as non-discovered, and mark the run as aborted.
+            // _dataAggregator.MarkAsAborted();
+        }
+
+        _parallelOperationManager.StartWork(runnableWorkloads, eventHandler, GetParallelEventHandler, InitializeDiscoverTestsOnConcurrentManager, DiscoverTestsOnConcurrentManager);
     }
 
     private ITestDiscoveryEventsHandler2 GetParallelEventHandler(ITestDiscoveryEventsHandler2 eventHandler, IProxyDiscoveryManager concurrentManager)
diff --git a/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyExecutionManager.cs b/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyExecutionManager.cs
index 792ddef3ce..aeaf4ec09a 100644
--- a/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyExecutionManager.cs
+++ b/src/Microsoft.TestPlatform.CrossPlatEngine/Client/Parallel/ParallelProxyExecutionManager.cs
@@ -115,7 +115,7 @@ public int StartTestRun(TestRunCriteria testRunCriteria, IInternalTestRunEventsH
             // _currentRunDataAggregator.MarkAsAborted();
         }
 
-        _parallelOperationManager.StartWork(workloads, eventHandler, GetParallelEventHandler, PrepareTestRunOnConcurrentManager, StartTestRunOnConcurrentManager);
+        _parallelOperationManager.StartWork(runnableWorkloads, eventHandler, GetParallelEventHandler, PrepareTestRunOnConcurrentManager, StartTestRunOnConcurrentManager);
 
         // Why 1? Because this is supposed to be a processId, and that is just the default that was chosen by someone before me,
         // and maybe is checked somewhere, but I don't see it checked in our codebase.