diff --git a/pym/cl_template.py b/pym/cl_template.py
index 25b1778..0e5ed80 100644
--- a/pym/cl_template.py
+++ b/pym/cl_template.py
@@ -417,7 +417,7 @@ class fileHeader(_terms):
                 else:
                     self.headerTerm = False
                     self.setError(_("incorrect header parameters - '%s'")\
-                    %"append=%s"%self.params["append"]
+                    %"append=%s"%self.params["append"])
         if not incorrectParams and self.params:
             incorrectParams = set(self.params.keys()) - set(self.allowParam)
         if incorrectParams: