diff --git a/gns3server/modules/dynamips/__init__.py b/gns3server/modules/dynamips/__init__.py
index b8053c3e..1592e9ce 100644
--- a/gns3server/modules/dynamips/__init__.py
+++ b/gns3server/modules/dynamips/__init__.py
@@ -560,8 +560,8 @@ class Dynamips(BaseManager):
             raise DynamipsError("Could not create Dynamips configs directory: {}".format(e))
 
         try:
-            with open(path, "w") as f:
-                f.write(content)
+            with open(path, "wb") as f:
+                f.write(content.encode("utf-8"))
         except OSError as e:
             raise DynamipsError("Could not create config file {}: {}".format(path, e))