diff --git a/application.py b/application.py
index 519bd8c..da85421 100755
--- a/application.py
+++ b/application.py
@@ -726,7 +726,8 @@ class Application(object):
     # running external programs
     def run_pipe(self, args, b, name='*Output*', switch=True, modename=None):
         pipe = Popen(args=args, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
-        pipe.stdin.write(b.make_string())
+        data = b.make_string().encode('utf-8')
+        pipe.stdin.write(data)
         pipe.stdin.close()
         output = pipe.stdout.read()
         status = pipe.wait()