diff --git a/draw/gen.go b/draw/gen.go
index 65a7123..822bb6a 100644
--- a/draw/gen.go
+++ b/draw/gen.go
@@ -877,8 +877,9 @@ func relName(s string) string {
 const (
 	codeRoot = `
 		func (z $receiver) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
-			// Try to simplify a Scale to a Copy.
-			if dr.Size() == sr.Size() {
+			// Try to simplify a Scale to a Copy when DstMask is not specified.
+			// If DstMask is not nil, Copy will call Scale back with same dr and sr, and cause stack overflow.
+			if dr.Size() == sr.Size() && (opts == nil || opts.DstMask == nil) {
 				Copy(dst, dr.Min, src, sr, op, opts)
 				return
 			}
diff --git a/draw/impl.go b/draw/impl.go
index 637887b..75498ad 100644
--- a/draw/impl.go
+++ b/draw/impl.go
@@ -11,8 +11,9 @@ import (
 )
 
 func (z nnInterpolator) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
-	// Try to simplify a Scale to a Copy.
-	if dr.Size() == sr.Size() {
+	// Try to simplify a Scale to a Copy when DstMask is not specified.
+	// If DstMask is not nil, Copy will call Scale back with same dr and sr, and cause stack overflow.
+	if dr.Size() == sr.Size() && (opts == nil || opts.DstMask == nil) {
 		Copy(dst, dr.Min, src, sr, op, opts)
 		return
 	}
@@ -1048,8 +1049,9 @@ func (nnInterpolator) transform_Image_Image_Src(dst Image, dr, adr image.Rectang
 }
 
 func (z ablInterpolator) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
-	// Try to simplify a Scale to a Copy.
-	if dr.Size() == sr.Size() {
+	// Try to simplify a Scale to a Copy when DstMask is not specified.
+	// If DstMask is not nil, Copy will call Scale back with same dr and sr, and cause stack overflow.
+	if dr.Size() == sr.Size() && (opts == nil || opts.DstMask == nil) {
 		Copy(dst, dr.Min, src, sr, op, opts)
 		return
 	}
diff --git a/draw/scale_test.go b/draw/scale_test.go
index 5e184c2..ea41940 100644
--- a/draw/scale_test.go
+++ b/draw/scale_test.go
@@ -551,6 +551,17 @@ func TestRectDstMask(t *testing.T) {
 	}
 }
 
+func TestDstMaskSameSizeCopy(t *testing.T) {
+	bounds := image.Rect(0, 0, 42, 42)
+	src := image.Opaque
+	dst := image.NewRGBA(bounds)
+	mask := image.NewRGBA(bounds)
+
+	Copy(dst, image.ZP, src, bounds, Src, &Options{
+		DstMask: mask,
+	})
+}
+
 // TODO: delete this wrapper type once Go 1.5 is released, where an
 // image.Rectangle implements image.Image.
 type rectImage image.Rectangle