diff --git a/grid.cc b/grid.cc
index 94f962cc6..0cff60990 100644
--- a/grid.cc
+++ b/grid.cc
@@ -1335,16 +1335,23 @@ auto get_coordboundary_distances_cylindrical2d(const std::array<double, 3> &pkt_
   }
 
   // z boundaries are the same as Cartesian
-  const double t_zcoordminboundary =
-      ((pktposgridcoord[1] - (pktvelgridcoord[1] * tstart)) /
-       ((grid::get_cellcoordmin(cellindex, 1)) - (pktvelgridcoord[1] * globals::tmin)) * globals::tmin) -
-      tstart;
-  d_coordminboundary[1] = CLIGHT_PROP * t_zcoordminboundary;
 
-  const double t_zcoordmaxboundary = ((pktposgridcoord[1] - (pktvelgridcoord[1] * tstart)) /
-                                      ((cellcoordmax[1]) - (pktvelgridcoord[1] * globals::tmin)) * globals::tmin) -
-                                     tstart;
-  d_coordmaxboundary[1] = CLIGHT_PROP * t_zcoordmaxboundary;
+  if ((pktvelgridcoord[1] * tstart) > pktposgridcoord[1]) {
+    d_coordminboundary[1] = -1;
+
+    const double t_zcoordmaxboundary = ((pktposgridcoord[1] - (pktvelgridcoord[1] * tstart)) /
+                                        ((cellcoordmax[1]) - (pktvelgridcoord[1] * globals::tmin)) * globals::tmin) -
+                                       tstart;
+    d_coordmaxboundary[1] = CLIGHT_PROP * t_zcoordmaxboundary;
+  } else {
+    const double t_zcoordminboundary =
+        ((pktposgridcoord[1] - (pktvelgridcoord[1] * tstart)) /
+         ((grid::get_cellcoordmin(cellindex, 1)) - (pktvelgridcoord[1] * globals::tmin)) * globals::tmin) -
+        tstart;
+    d_coordminboundary[1] = CLIGHT_PROP * t_zcoordminboundary;
+
+    d_coordmaxboundary[1] = -1;
+  }
 
   return {d_coordminboundary, d_coordmaxboundary};
 }
@@ -2486,12 +2493,6 @@ auto get_totmassradionuclide(const int z, const int a) -> double {
     std::tie(d_coordminboundary, d_coordmaxboundary) = get_coordboundary_distances_cylindrical2d(
         pos, dir, pktposgridcoord, pktvelgridcoord, cellindex, tstart, cellcoordmax);
 
-    if ((pktvelgridcoord[1] * tstart) > pktposgridcoord[1]) {
-      d_coordminboundary[1] = -1;
-    } else {
-      d_coordmaxboundary[1] = -1;
-    }
-
   } else if constexpr (GRID_TYPE == GridType::CARTESIAN3D) {
     // There are six possible boundary crossings. Each of the three
     // cartesian coordinates may be taken in turn. For x, the packet