diff --git a/Buildings/Resources/C-Sources/cfdSendStopCommand.c b/Buildings/Resources/C-Sources/cfdSendStopCommand.c
index 93cf78653b1..77bf3d3b9bf 100644
--- a/Buildings/Resources/C-Sources/cfdSendStopCommand.c
+++ b/Buildings/Resources/C-Sources/cfdSendStopCommand.c
@@ -149,6 +149,9 @@ void cfdSendStopCommand(void *thread) {
   }
   if (cosim != NULL){
     free(cosim);
+    /* If it is not explicitly set to NULL - then the check in cfdcosim() 
+       will fail if a second simulation is performed. */
+    cosim = NULL;
   }
 
 } /* End of cfdSendStopCommand*/