diff --git a/swfiles/@spinw/fitspec.m b/swfiles/@spinw/fitspec.m
index 1e55545d0..fb7f6882d 100644
--- a/swfiles/@spinw/fitspec.m
+++ b/swfiles/@spinw/fitspec.m
@@ -362,6 +362,10 @@
         'tid',0,'optMem',param.optmem,'gtensor',any(obj.single_ion.g),'fid',0);
     % calculate neutron scattering cross section
     spec = sw_neutron(spec,'n',data.n,'pol',data.corr.type{1}(1) > 1);
+    if size(obj.twin.vol, 2) > 1
+        % Need to include the original SpinW for sw_egrid to handle twins correctly.
+        spec.obj = obj;
+    end
     % bin the data along energy
     try
         spec = sw_egrid(spec,'component',data.corr,'Evect',param.Evect,'imagChk',param.imagChk);