diff --git a/R/scale-discrete-.R b/R/scale-discrete-.R
index bb1518746f..a5ff3289a4 100644
--- a/R/scale-discrete-.R
+++ b/R/scale-discrete-.R
@@ -19,8 +19,9 @@
 #' @param continuous.limits One of:
 #'   * `NULL` to use the default scale range
 #'   * A numeric vector of length two providing a display range for the scale.
-#'   * A function that accepts the existing continuous limits and returns a
-#'     numeric vector of length two.
+#'   Use `NA` to refer to the existing minimum or maximum.
+#'   * A function that accepts the limits and returns a numeric vector of
+#'   length two.
 #' @rdname scale_discrete
 #' @family position scales
 #' @seealso
diff --git a/R/scale-expansion.R b/R/scale-expansion.R
index ce61a1c5e3..9c682eeaa6 100644
--- a/R/scale-expansion.R
+++ b/R/scale-expansion.R
@@ -180,8 +180,7 @@ expand_limits_discrete <- function(limits, expand = expansion(0, 0), coord_limit
     check_numeric(continuous_limits, arg = "continuous.limits")
     check_length(continuous_limits, 2L, arg = "continuous.limits")
     missing <- is.na(continuous_limits)
-    limits       <- range(ifelse(missing, limits, continuous_limits))
-    coord_limits <- range(ifelse(missing, coord_limits, continuous_limits))
+    limits  <- ifelse(missing, range(limits), continuous_limits)
   }
 
   limit_info <- expand_limits_discrete_trans(
diff --git a/man/scale_discrete.Rd b/man/scale_discrete.Rd
index 7e6e251980..19e1df99fb 100644
--- a/man/scale_discrete.Rd
+++ b/man/scale_discrete.Rd
@@ -114,8 +114,9 @@ expand the scale by 5\% on each side for continuous variables, and by
 \itemize{
 \item \code{NULL} to use the default scale range
 \item A numeric vector of length two providing a display range for the scale.
-\item A function that accepts the existing continuous limits and returns a
-numeric vector of length two.
+Use \code{NA} to refer to the existing minimum or maximum.
+\item A function that accepts the limits and returns a numeric vector of
+length two.
 }}
 }
 \description{