diff --git a/R/scale-.r b/R/scale-.r
index f8f20f9842..56c036dd29 100644
--- a/R/scale-.r
+++ b/R/scale-.r
@@ -560,6 +560,17 @@ check_breaks_labels <- function(breaks, labels) {
   TRUE
 }
 
+default_transform <- function(self, x) {
+  new_x <- self$trans$transform(x)
+  axis <- if ("x" %in% self$aesthetics) "x" else "y"
+  check_transformation(x, new_x, self$scale_name, axis)
+  new_x
+}
+
+has_default_transform <- function(scale) {
+  transform_method <- environment(scale$transform)$f
+  identical(default_transform, transform_method) || identical(identity, transform_method)
+}
 
 #' @rdname ggplot2-ggproto
 #' @format NULL
@@ -589,12 +600,7 @@ ScaleContinuous <- ggproto("ScaleContinuous", Scale,
     !has_data && !has_limits
   },
 
-  transform = function(self, x) {
-    new_x <- self$trans$transform(x)
-    axis <- if ("x" %in% self$aesthetics) "x" else "y"
-    check_transformation(x, new_x, self$scale_name, axis)
-    new_x
-  },
+  transform = default_transform,
 
   map = function(self, x, limits = self$get_limits()) {
     x <- self$rescale(self$oob(x, range = limits), limits)
@@ -819,9 +825,7 @@ ScaleDiscrete <- ggproto("ScaleDiscrete", Scale,
     self$range$train(x, drop = self$drop, na.rm = !self$na.translate)
   },
 
-  transform = function(x) {
-    x
-  },
+  transform = identity,
 
   map = function(self, x, limits = self$get_limits()) {
     n <- sum(!is.na(limits))
@@ -1001,12 +1005,7 @@ ScaleBinned <- ggproto("ScaleBinned", Scale,
     self$range$train(x)
   },
 
-  transform = function(self, x) {
-    new_x <- self$trans$transform(x)
-    axis <- if ("x" %in% self$aesthetics) "x" else "y"
-    check_transformation(x, new_x, self$scale_name, axis)
-    new_x
-  },
+  transform = default_transform,
 
   map = function(self, x, limits = self$get_limits()) {
     if (self$after.stat) {
diff --git a/R/scales-.r b/R/scales-.r
index 1537ff0f65..cb1e784670 100644
--- a/R/scales-.r
+++ b/R/scales-.r
@@ -85,8 +85,8 @@ scales_transform_df <- function(scales, df) {
   # if the scale contains no trans or the trans is of identity, it doesn't need
   # to be transformed.
   idx_skip <- vapply(scales$scales, function(x) {
-    is.null(x$trans) ||
-      identical(x$trans$transform, identity)
+    has_default_transform(x) &&
+    (is.null(x$trans) || identical(x$trans$transform, identity))
   }, logical(1L))
   scale_list <- scales$scales[!idx_skip]