diff --git a/boxmox/experiment.py b/boxmox/experiment.py
index d785dbe90a67fe346ba2f4a13e29f4dbe4e9662c..fb99fb4f0d912f7cd3f14f1c42caab65991ae034 100644
--- a/boxmox/experiment.py
+++ b/boxmox/experiment.py
@@ -227,6 +227,10 @@ class Experiment:
         :param bool dumbOutput: Only load references to output files, instead of loading data? (faster, but not usable for analysis)
         :param bool asynchronous: Run asynchronous?
         '''
+        if asynchronous:
+            if self.running:
+                return
+        
         self.namelist.write(os.path.join(self.path, 'BOXMOX.nml'))
 
         for type in self.input: