diff --git a/python/dune/perftool/sumfact/tabulation.py b/python/dune/perftool/sumfact/tabulation.py
index 68277a18a48c6aefc4be6075e42d1bbb22e6b950..daeabf9005cbff9c5917185b5711ceb6cb4342a3 100644
--- a/python/dune/perftool/sumfact/tabulation.py
+++ b/python/dune/perftool/sumfact/tabulation.py
@@ -146,7 +146,7 @@ class BasisTabulationMatrixArray(BasisTabulationMatrixBase):
         self.width = width
 
     def __str__(self):
-        return "_".join((t._shortname for t in self.tabs))
+        return "Theta{}".format("_".join((t._shortname for t in self.tabs)))
 
     @property
     def quadrature_size(self):