diff --git a/corsika/detail/modules/pythia8/NeutrinoInteraction.inl b/corsika/detail/modules/pythia8/NeutrinoInteraction.inl
index 183d360c27848da8d5bae7902041dc8742db048d..9bb135ad1097669761dd0c4f53772bbd12c8f66f 100644
--- a/corsika/detail/modules/pythia8/NeutrinoInteraction.inl
+++ b/corsika/detail/modules/pythia8/NeutrinoInteraction.inl
@@ -116,16 +116,17 @@ namespace corsika::pythia8 {
       double Q2min = minQ2_ / 1_GeV;
 
       // Set up incoming beams, for frame with unequal beam energies.
+      // projectile is along -z
       pythiaMain_.readString("Beams:frameType = 2");
       // BeamA = proton.
-      pythiaMain_.readString("Beams:idB = 2212");
-      pythiaMain_.settings.parm("Beams:eB", eProton);
+      pythiaMain_.readString("Beams:idA = 2212");
+      pythiaMain_.settings.parm("Beams:eA", eProton);
       // BeamB = electron.
       int const idNow = static_cast<int>(get_PDG(projectileId));
-      pythiaMain_.readString("Beams:idA = 12");
+      pythiaMain_.readString("Beams:idB = 12");
 
       // pythiaMain_.settings.parm("Beams:idA", idNow);
-      pythiaMain_.settings.parm("Beams:eA", eElectron);
+      pythiaMain_.settings.parm("Beams:eB", eElectron);
 
       // Set up DIS process within some phase space.
       // Neutral current (with gamma/Z interference).