diff --git a/vignettes/articles/phytools2.Rmd b/vignettes/articles/phytools2.Rmd
index 61260e2..b05b205 100644
--- a/vignettes/articles/phytools2.Rmd
+++ b/vignettes/articles/phytools2.Rmd
@@ -71,7 +71,9 @@ ncbi_tree$Do(function(node) {
 
 ```{r}
 Attribute_group_var <- unique(phys_data_ready$Attribute_group)
+Attribute_group_var <- Attribute_group_var[!is.na(Attribute_group_var)]
 Attribute_type_var <- unique(phys_data_ready$Attribute_type)
+Attribute_type_var <- Attribute_type_var[!is.na(Attribute_type_var)]
 ncbi_tree$Do(
     function(node) taxPool(node = node, grp = Attribute_group_var, typ = Attribute_type_var), 
     traversal = 'post-order'