diff --git a/include/dspatch/Circuit.h b/include/dspatch/Circuit.h
index 684a954e..fe0c4a8d 100644
--- a/include/dspatch/Circuit.h
+++ b/include/dspatch/Circuit.h
@@ -634,11 +634,6 @@ inline void Circuit::SetThreadCount( int threadCount )
 {
     PauseAutoTick();
 
-    if ( _threadCount == 0 && threadCount != 0 )
-    {
-        _circuitDirty = true;
-    }
-
     _threadCount = threadCount;
 
     // stop all threads
@@ -799,27 +794,24 @@ inline void Circuit::_Optimize()
     }
 
     // scan for optimal parallel order -> update _componentsParallel
-    if ( _threadCount != 0 )
-    {
-        std::vector<std::vector<DSPatch::Component*>> componentsMap;
-        componentsMap.reserve( _components.size() );
+    std::vector<std::vector<DSPatch::Component*>> componentsMap;
+    componentsMap.reserve( _components.size() );
 
-        int scanPosition;
-        for ( auto component : _components )
-        {
-            component->ScanParallel( componentsMap, scanPosition );
-        }
-        for ( auto component : _components )
-        {
-            component->EndScan();
-        }
+    int scanPosition;
+    for ( auto component : _components )
+    {
+        component->ScanParallel( componentsMap, scanPosition );
+    }
+    for ( auto component : _components )
+    {
+        component->EndScan();
+    }
 
-        _componentsParallel.clear();
-        _componentsParallel.reserve( _components.size() );
-        for ( auto& componentsMapEntry : componentsMap )
-        {
-            _componentsParallel.insert( _componentsParallel.end(), componentsMapEntry.begin(), componentsMapEntry.end() );
-        }
+    _componentsParallel.clear();
+    _componentsParallel.reserve( _components.size() );
+    for ( auto& componentsMapEntry : componentsMap )
+    {
+        _componentsParallel.insert( _componentsParallel.end(), componentsMapEntry.begin(), componentsMapEntry.end() );
     }
 
     // clear _circuitDirty flag
diff --git a/include/dspatch/Component.h b/include/dspatch/Component.h
index 42f4d4cb..5dcc32a9 100644
--- a/include/dspatch/Component.h
+++ b/include/dspatch/Component.h
@@ -491,10 +491,10 @@ inline void Component::ScanParallel( std::vector<std::vector<DSPatch::Component*
     }
 
     // insert component at _scanPosition
-    if ( _scanPosition == (int)componentsMap.size() )
+    while ( (int)componentsMap.size() <= _scanPosition )
     {
         componentsMap.emplace_back( std::vector<DSPatch::Component*>{} );
-        componentsMap[_scanPosition].reserve( componentsMap.capacity() );
+        componentsMap.back().reserve( componentsMap.capacity() );
     }
     componentsMap[_scanPosition].emplace_back( this );
 }