diff --git a/bfps/_base.py b/bfps/_base.py
index ad8fcca37c0a739f9b8f895aaee7175025cd65bb..395c423e9b8a0e7bc3308acd917ea1eac01148b4 100644
--- a/bfps/_base.py
+++ b/bfps/_base.py
@@ -143,7 +143,7 @@ class _base(object):
                     ofile[group + '/' + k] = parameters[k]
             else:
                 if (type(parameters[k]) == str) and (sys.version_info[0] == 3):
-                    ofile[group + '/' + k][:] = bytes(parameters[k], 'ascii')
+                    ofile[group + '/' + k][...] = bytes(parameters[k], 'ascii')
                 else:
                     ofile[group + '/' + k][...] = parameters[k]
         ofile.close()