diff --git a/R/scale-.R b/R/scale-.R
index 7cae5da74b..66a0c91de4 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -714,7 +714,11 @@ ScaleContinuous <- ggproto("ScaleContinuous", Scale,
     pal <- self$palette(uniq)
     scaled <- pal[match(x, uniq)]
 
-    ifelse(!is.na(scaled), scaled, self$na.value)
+    if (!anyNA(scaled)) {
+      return(scaled)
+    }
+
+    vec_assign(scaled, is.na(scaled), self$na.value)
   },
 
   rescale = function(self, x, limits = self$get_limits(), range = limits) {
diff --git a/R/scale-continuous.R b/R/scale-continuous.R
index 8a681c2f20..9b0c8ec82c 100644
--- a/R/scale-continuous.R
+++ b/R/scale-continuous.R
@@ -142,7 +142,10 @@ ScaleContinuousPosition <- ggproto("ScaleContinuousPosition", ScaleContinuous,
   # can tell the difference between continuous and discrete data.
   map = function(self, x, limits = self$get_limits()) {
     scaled <- as.numeric(self$oob(x, limits))
-    ifelse(!is.na(scaled), scaled, self$na.value)
+    if (!anyNA(scaled)) {
+      return(scaled)
+    }
+    vec_assign(scaled, is.na(scaled), self$na.value)
   },
   break_info = function(self, range = NULL) {
     breaks <- ggproto_parent(ScaleContinuous, self)$break_info(range)