diff --git a/R/data_summary.R b/R/data_summary.R
index 7662d0c94..546c47659 100644
--- a/R/data_summary.R
+++ b/R/data_summary.R
@@ -5,9 +5,9 @@
 #' data frame or a matrix.
 #'
 #' @param x A (grouped) data frame.
-#' @param by Optional character string, indicating the name of a variable in `x`.
-#' If supplied, the data will be split by this variable and summary statistics
-#' will be computed for each group.
+#' @param by Optional character string, indicating the names of one or more
+#' variables in the data frame. If supplied, the data will be split by these
+#' variables and summary statistics will be computed for each group.
 #' @param remove_na Logical. If `TRUE`, missing values are omitted from the
 #' grouping variable. If `FALSE` (default), missing values are included as a
 #' level in the grouping variable.
diff --git a/man/data_summary.Rd b/man/data_summary.Rd
index 24cfa1a9f..82d154175 100644
--- a/man/data_summary.Rd
+++ b/man/data_summary.Rd
@@ -18,9 +18,9 @@ and the function to compute the summary statistic. Example:
 as a character string, e.g. \code{"mean_sepal_width = mean(Sepal.Width)"}. The
 summary function \code{n()} can be used to count the number of observations.}
 
-\item{by}{Optional character string, indicating the name of a variable in \code{x}.
-If supplied, the data will be split by this variable and summary statistics
-will be computed for each group.}
+\item{by}{Optional character string, indicating the names of one or more
+variables in the data frame. If supplied, the data will be split by these
+variables and summary statistics will be computed for each group.}
 
 \item{remove_na}{Logical. If \code{TRUE}, missing values are omitted from the
 grouping variable. If \code{FALSE} (default), missing values are included as a