diff --git a/src/laser_geometry.cpp b/src/laser_geometry.cpp
index 0b05a2e..3ec836c 100644
--- a/src/laser_geometry.cpp
+++ b/src/laser_geometry.cpp
@@ -623,6 +623,12 @@ const boost::numeric::ublas::matrix<double>& LaserProjection::getUnitVectors_(do
           {
             offset_shift = cloud_out.fields[i + 1].offset - cloud_out.fields[i].offset;
           }
+          else
+          {
+            //we know that the index is the last field... but the shift is still important
+            //for computing the point_step and data size
+            offset_shift = 4;
+          }
         }
       }