diff --git a/modules/util/abi_surfrad.py b/modules/util/abi_surfrad.py
index 6c2037125c1c54c18544f8bc9ddf48dd0351b1cd..1e371886f2ed9608a191a0a00ee01088bf5c9423 100644
--- a/modules/util/abi_surfrad.py
+++ b/modules/util/abi_surfrad.py
@@ -75,7 +75,7 @@ def process_cloud_frac(grd_k):
 
     grd_by_cat = get_cloud_frac_5cat(grd_k)
     # if at least 20% mixed pass
-    keep_mix = np.where(keep, 0 < grd_by_cat < 4, False)
+    keep_mix = np.where(keep, np.logical_and(grd_by_cat > 0, grd_by_cat < 4), False)
     frac_mix = np.sum(keep_mix)/num_keep
     if frac_mix < 0.20:
         return None