diff --git a/rfc3161/types.py b/rfc3161/types.py
index bbafe18..330a695 100644
--- a/rfc3161/types.py
+++ b/rfc3161/types.py
@@ -39,7 +39,7 @@ class TimeStampReq(univ.Sequence):
 # Reponse
 
 class PKIFreeText(univ.SequenceOf):
-    componentType = char.UTF8String
+    componentType = char.UTF8String()
     sizeSpec = univ.SequenceOf.sizeSpec + constraint.ValueSizeConstraint(1, MAX)
 
 class PKIStatus(univ.Integer):