diff --git a/pylot/core/analysis/magnitude.py b/pylot/core/analysis/magnitude.py
index a7a2befa..6c2ab843 100644
--- a/pylot/core/analysis/magnitude.py
+++ b/pylot/core/analysis/magnitude.py
@@ -306,7 +306,8 @@ def calcMoMw(wfstream, w0, rho, vp, delta, inv):
     return Mo, Mw
 
 
-def calcsourcespec(wfstream, onset, inventory, vp, delta, azimuth, incidence, qp, iplot):
+def calcsourcespec(wfstream, onset, metadata, vp, delta, azimuth, incidence,
+                   qp, iplot):
     '''
     Subfunction to calculate the source spectrum and to derive from that the plateau
     (usually called omega0) and the corner frequency assuming Aki's omega-square
@@ -353,7 +354,9 @@ def calcsourcespec(wfstream, onset, inventory, vp, delta, azimuth, incidence, qp
     data = Data()
     wf_copy = wfstream.copy()
 
-    [cordat, restflag] = restitute_data(wf_copy, inventory)
+    invtype, inventory = metadata
+
+    [cordat, restflag] = restitute_data(wf_copy, invtype, inventory)
     if restflag is True:
         zdat = cordat.select(component="Z")
         if len(zdat) == 0: