diff --git a/bmp/reader_test.go b/bmp/reader_test.go
index fd6ff64..91b4391 100644
--- a/bmp/reader_test.go
+++ b/bmp/reader_test.go
@@ -15,7 +15,7 @@ import (
 
 const testdataDir = "../testdata/"
 
-func compare(t *testing.T, img0, img1 image.Image) error {
+func compare(img0, img1 image.Image) error {
 	b := img1.Bounds()
 	if !b.Eq(img0.Bounds()) {
 		return fmt.Errorf("wrong image size: want %s, got %s", img0.Bounds(), b)
@@ -67,7 +67,7 @@ func TestDecode(t *testing.T) {
 			continue
 		}
 
-		if err := compare(t, img0, img1); err != nil {
+		if err := compare(img0, img1); err != nil {
 			t.Errorf("%s: %v", tc, err)
 			continue
 		}
diff --git a/bmp/writer_test.go b/bmp/writer_test.go
index 1643e4d..8b573a8 100644
--- a/bmp/writer_test.go
+++ b/bmp/writer_test.go
@@ -64,7 +64,7 @@ func TestEncode(t *testing.T) {
 			continue
 		}
 
-		err = compare(t, img0, img1)
+		err = compare(img0, img1)
 		if err != nil {
 			t.Errorf("%s: Compare BMP: %v", tc, err)
 			continue
@@ -88,7 +88,7 @@ func TestEncode(t *testing.T) {
 		// the conversion process is lossy.
 		img3 := convertToNRGBA(rgba)
 
-		err = compare(t, img3, img2)
+		err = compare(img3, img2)
 		if err != nil {
 			t.Errorf("%s: Compare pre-multiplied BMP: %v", tc, err)
 		}