diff --git a/lib/potential/gm_data.cpp b/lib/potential/gm_data.cpp
index 2f3916d..2ca6a69 100644
--- a/lib/potential/gm_data.cpp
+++ b/lib/potential/gm_data.cpp
@@ -175,12 +175,18 @@ void gctl::read_Swarm_shc(std::string file, array<shc_data> &SHCs, int &spline_o
         tio.get_column(vals, i + 3);
         for (size_t j = 0; j < rnum; j++)
         {
-            if (mid[j] >= 0)
+            if (mid[j] > 0)
             {
                 id = nid[j]*(nid[j] + 1)/2 + mid[j];
                 SHCs[i].Snm[id] = vals[j];
                 SHCs[i].Cnm[id] = vals[j + 1];
             }
+            else if (mid[j] == 0)
+            {
+                id = nid[j]*(nid[j] + 1)/2;
+                SHCs[i].Snm[id] = vals[j];
+                SHCs[i].Cnm[id] = 0.0;
+            }
         }
     }
     return;