diff --git a/src/simulation/Simulation.cpp b/src/simulation/Simulation.cpp
index 52c5a4ddd..0e92e45f0 100644
--- a/src/simulation/Simulation.cpp
+++ b/src/simulation/Simulation.cpp
@@ -4351,8 +4351,18 @@ killed:
 						continue;
 					}
 
-					if (TYP(r))
-						parts[i].ctype &= elements[TYP(r)].PhotonReflectWavelengths;
+					if (t == PT_PHOT)
+					{
+						auto mask = elements[TYP(r)].PhotonReflectWavelengths;
+						if (TYP(r) == PT_LITH)
+						{
+							int wl_bin = parts[ID(r)].ctype / 4;
+							if (wl_bin < 0) wl_bin = 0;
+							if (wl_bin > 25) wl_bin = 25;
+							mask = (0x1F << wl_bin);
+						}
+						parts[i].ctype &= mask;
+					}
 
 					if (get_normal_interp(t, parts[i].x, parts[i].y, parts[i].vx, parts[i].vy, &nrx, &nry))
 					{