diff --git a/qpms/qpms_c.pyx b/qpms/qpms_c.pyx
index 47d3b52..5a6e203 100644
--- a/qpms/qpms_c.pyx
+++ b/qpms/qpms_c.pyx
@@ -425,6 +425,7 @@ cdef class ScatteringSystem:
         cdef _ScatteringSystemAtOmega pyssw = _ScatteringSystemAtOmega()
         pyssw.ssw = qpms_scatsys_at_omega(self.s, omega)
         pyssw.ss_pyref = self
+        return pyssw
 
     def __dealloc__(self):
         if(self.s):
diff --git a/qpms/scatsystem.c b/qpms/scatsystem.c
index b6b1149..febef46 100644
--- a/qpms/scatsystem.c
+++ b/qpms/scatsystem.c
@@ -280,7 +280,7 @@ qpms_scatsys_at_omega_t *qpms_scatsys_apply_symmetry(const qpms_scatsys_t *orig,
 	ss->tm[ss->tm_count].tmgi = ss->tm[tmi].tmgi;
         qpms_tmatrix_operation_compose_chain_init(&(ss->tm[ss->tm_count].op), 2, 1);
         struct qpms_tmatrix_operation_compose_chain * const o = &(ss->tm[ss->tm_count].op.op.compose_chain);
-        o->ops[0] = & ss->tm[tmj].op; // Let's just borrow this
+        o->ops[0] = & ss->tm[tmi].op; // Let's just borrow this
         o->ops_owned[0] = false;
         o->opmem[0].typ = QPMS_TMATRIX_OPERATION_LRMATRIX;
         o->opmem[0].op.lrmatrix.m = m;
@@ -505,6 +505,7 @@ qpms_scatsys_at_omega_t *qpms_scatsys_at_omega(const qpms_scatsys_t *ss,
   ssw->ss = ss;
   ssw->medium = qpms_epsmu_generator_eval(ss->medium, omega);
   ssw->wavenumber = qpms_wavenumber(omega, ssw->medium);
+  QPMS_CRASHING_CALLOC(ssw->tm, ss->tm_count, sizeof(*ssw->tm));
   qpms_tmatrix_t **tmatrices_preop;
   QPMS_CRASHING_CALLOC(tmatrices_preop, ss->tmg_count, sizeof(*tmatrices_preop));
   for (qpms_ss_tmgi_t tmgi = 0; tmgi < ss->tmg_count; ++tmgi)