diff --git a/force_bdss/io/workflow_reader.py b/force_bdss/io/workflow_reader.py
index 92e6b3909de90bbe7469dde22627a40f30bcba38..dd9687e2f28c87696caa8e4f047fbfcd60e3fc56 100644
--- a/force_bdss/io/workflow_reader.py
+++ b/force_bdss/io/workflow_reader.py
@@ -206,7 +206,7 @@ class WorkflowReader(HasStrictTraits):
                 except KeyError:
                     raise MissingPluginException(
                         "Could not read file. "
-                        "The plugin responsible for the missing data source"
+                        "The plugin responsible for the missing data source "
                         "key '{}' may be missing or broken.".format(ds_id)
                     )