diff --git a/qpms/cytmatrices.pxd b/qpms/cytmatrices.pxd
index 183ec29..6e462b3 100644
--- a/qpms/cytmatrices.pxd
+++ b/qpms/cytmatrices.pxd
@@ -1,5 +1,5 @@
 cimport numpy as np
-from .qpms_cdefs cimport qpms_tmatrix_t, cdouble, qpms_tmatrix_interpolator_t
+from .qpms_cdefs cimport qpms_tmatrix_t, cdouble, qpms_tmatrix_interpolator_t, qpms_tmatrix_generator_t
 from .cybspec cimport BaseSpec
 
 cdef class TMatrixInterpolator:
diff --git a/qpms/qpms_c.pyx b/qpms/qpms_c.pyx
index 7f27b17..ef5554c 100644
--- a/qpms/qpms_c.pyx
+++ b/qpms/qpms_c.pyx
@@ -320,7 +320,7 @@ cdef class ScatteringSystem:
     cdef qpms_scatsys_t *s
     cdef qpms_tmatrix_function_t *tmg # this will ultimately contain pointers to stuff in basespecs and tmgens.
 
-    def __cinit__(self, particles, FinitePointGroup sym):
+    def __cinit__(self, particles, FinitePointGroup sym, omega):
         '''TODO doc.
         Takes the particles (which have to be a sequence of instances of Particle),
         fills them together with their t-matrices to the "proto-qpms_scatsys_t"
@@ -540,6 +540,16 @@ cdef class ScatteringSystem:
     def scatter_solver(self, double k, iri=None):
         return ScatteringMatrix(self, k, iri)
 
+cdef class ScatteringSystemAtOmega:
+    '''
+    Wrapper over the C qpms_scatsys_at_omega_t structure
+    that keeps the T-matrix and background data evaluated
+    at specific frequency.
+    '''
+    cdef qpms_scatsys_at_omega_t ssw
+
+    pass #TODO
+
 cdef class ScatteringMatrix:
     '''
     Wrapper over the C qpms_ss_LU structure that keeps the factorised mode problem matrix.