diff --git a/find_exons.py b/find_exons.py
index c31c063..9bd28dd 100644
--- a/find_exons.py
+++ b/find_exons.py
@@ -84,6 +84,7 @@ def check_existing_input_files(args):
 		#print('working with a list of genes')
 		#genes_of_interest = args.genes_of_interest
 		print('please provide only one file with genes of interest')
+		sys.exit()
 
 	return genes_of_interest