diff --git a/src/main.py b/src/main.py
index 6f0db8d..0d56392 100644
--- a/src/main.py
+++ b/src/main.py
@@ -43,6 +43,12 @@
     def start(self):
         print "[XOS-TOSCA] Starting"
 
+        # Remove generated TOSCA and KEYS that may have been downloaded by a previous session. This is done here, rather
+        # than in the generator, to cover the case where the TOSCA engine is restarted and a web request is received
+        # and processed before generate_tosca() has completed. 
+        TOSCA_Generator().clean()
+        TOSCA_Generator().clean_keys()
+
         grpc_setup = GRPC_Client().start()
         grpc_setup.addCallback(self.generate_tosca)