diff --git a/src/wrf/interp.py b/src/wrf/interp.py
index 8e7fc57..32b851d 100755
--- a/src/wrf/interp.py
+++ b/src/wrf/interp.py
@@ -90,7 +90,7 @@ def interplevel(field3d, vert, desiredlev, missing=default_fill(np.float64),
             wrfin = Dataset("wrfout_d02_2010-06-13_21:00:00")
 
             rh = getvar(wrfin, "rh")
-            z = getvar(wrfin, "z")
+            z = getvar(wrfin, "z", msl=False)
             pblh = getvar(wrfin, "PBLH")
 
             rh_pblh = interplevel(rh, z, pblh)