diff --git a/reacnetgenerator/utils.py b/reacnetgenerator/utils.py
index 16870c2c4..1682fb1e1 100644
--- a/reacnetgenerator/utils.py
+++ b/reacnetgenerator/utils.py
@@ -49,7 +49,7 @@ def check(self):
 
     def flush(self):
         if self.buff:
-            self.f.write(self.sep.join(self.buff))
+            self.f.writelines([self.sep.join(self.buff), self.sep])
             self.buff[:] = []
 
     def __enter__(self):