diff --git a/pykat/finesse.py b/pykat/finesse.py
index 83bf3b32babb2efc1cb914d148581ee6e8763c67..959a7f760fc0df525048d8bfdb62cb8a8b4517e2 100644
--- a/pykat/finesse.py
+++ b/pykat/finesse.py
@@ -1687,7 +1687,8 @@ class kat(object):
                                         qx = spqx[0].split("=")[1].replace('i','j').replace(' ','') 
                                         qy = spqy[0].split("=")[1].replace('i','j').replace(' ','') 
                                         
-                                        traceData[-1][node_name] = (pykat.beam_param(q=complex(qx)), pykat.beam_param(q=complex(qy)))
+                                        traceData[-1][node_name] = (pykat.beam_param(q=complex(qx),wavelength=self.lambda0),
+                                                                    pykat.beam_param(q=complex(qy),wavelength=self.lambda0))
                             
                         finally:
                             ifile.close()