diff --git a/NAMESPACE b/NAMESPACE
index 3596a04..06e32cd 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -75,6 +75,7 @@
 importFrom(plotly,ggplotly)
 importFrom(purrr,map_dfr)
 importFrom(stats,prop.test)
+importFrom(tibble,add_column)
 importFrom(tibble,as_tibble)
 importFrom(tibble,remove_rownames)
 importFrom(tibble,rownames_to_column)
diff --git a/R/highcharter-helper.R b/R/highcharter-helper.R
index 3933e88..2d4d7c1 100644
--- a/R/highcharter-helper.R
+++ b/R/highcharter-helper.R
@@ -4,6 +4,7 @@
 #' \bold{Warning:} This function may be moved to a new package.
 #'
 #' @import highcharter
+#' @importFrom tibble add_column
 #' @export
 #'
 #' @param df data frame like the value of a \code{\link{frequencyQuery}}
@@ -44,7 +45,7 @@
     { if(! as.alternatives) ipm(.) else RKorAPClient::percent(.) }
 
   if (!"year" %in% colnames(df)) {
-    df <- df %>% mutate(year = as.integer(queryStringToLabel(df$vc, pubDateOnly = TRUE)))
+    df <- df %>% add_column(year = as.integer(queryStringToLabel(df$vc, pubDateOnly = TRUE)))
   }
   if (!"condition" %in% colnames(df)) {
     if (length(base::unique(df$query)) > 1) {
@@ -56,7 +57,7 @@
     } else {
       if (length(base::unique(queryStringToLabel(df$vc, excludePubDate = TRUE ))) > 1) {
         title <- base::unique(df$query)
-        df <- df %>% mutate(condition = queryStringToLabel(vc, excludePubDate = TRUE ))
+        df <- df %>% add_column(condition = queryStringToLabel(vc, excludePubDate = TRUE ))
       } else {
         df <- df %>% mutate(condition = query)
       }