diff --git a/flopy/modpath/mp6sim.py b/flopy/modpath/mp6sim.py
index 069ef5f66..4170aca68 100644
--- a/flopy/modpath/mp6sim.py
+++ b/flopy/modpath/mp6sim.py
@@ -561,7 +561,7 @@ def _write_particle_data_with_pandas(self, data, float_format):
 
         # write particle data
         print("writing loc particle data")
-        data.drop("groupname", 1, inplace=True)
+        data.drop(labels="groupname", axis=1, inplace=True)
         data.to_csv(
             loc_path,
             sep=" ",