diff --git a/lib/galaxy/tools/parameters/basic.py b/lib/galaxy/tools/parameters/basic.py
index a6f830e746a..8f64a80c050 100644
--- a/lib/galaxy/tools/parameters/basic.py
+++ b/lib/galaxy/tools/parameters/basic.py
@@ -1913,7 +1913,7 @@ class DataToolParameter(BaseDataToolParameter):
             ref = getattr(ref, attribute)
         if call_attribute:
             ref = ref()
-        return ref
+        return str(ref)
 
     def to_dict(self, trans, other_values={}):
         # create dictionary and fill default parameters