diff --git a/nifty/operators/propagator_operator/harmonic_propagator_operator.py b/nifty/operators/propagator_operator/harmonic_propagator_operator.py
index 3ad6501fe217cd4610ef7e1b8787aeb7f3eb4b0e..908e2e372f992dbd0c7afc7ce8fdbc0c62c94833 100644
--- a/nifty/operators/propagator_operator/harmonic_propagator_operator.py
+++ b/nifty/operators/propagator_operator/harmonic_propagator_operator.py
@@ -46,9 +46,21 @@ class HarmonicPropagatorOperator(InvertibleOperatorMixin, EndomorphicOperator):
             (default:ConjugateGradient)
         preconditioner : Field
             numerical preconditioner to speed up convergence
+        default_spaces : tuple of ints *optional*
+            Defines on which space(s) of a given field the Operator acts by
+            default (default: None)
 
     Attributes
     ----------
+    domain : tuple of DomainObjects, i.e. Spaces and FieldTypes
+        The domain on which the Operator's input Field lives.
+    target : tuple of DomainObjects, i.e. Spaces and FieldTypes
+        The domain in which the outcome of the operator lives. As the Operator
+        is endomorphic this is the same as its domain.
+    unitary : boolean
+        Indicates whether the Operator is unitary or not.
+    self_adjoint : boolean
+        Indicates whether the operator is self_adjoint or not.
 
     Raises
     ------