diff --git a/doc.go b/doc.go
index 9b88de4e0..bb4a92945 100644
--- a/doc.go
+++ b/doc.go
@@ -34,7 +34,9 @@
 //
 //     func main() {
 //         // Call ebiten.Run to start your game loop.
-//         ebiten.Run(update, 320, 240, 2, "Your game's title")
+//         if err := ebiten.Run(update, 320, 240, 2, "Your game's title"); err != nil {
+//             log.Fatal(err)
+//         }
 //     }
 //
 // The EBITEN_SCREENSHOT_KEY environment variable specifies the key
diff --git a/image.go b/image.go
index 4260b7fde..e0fe5543f 100644
--- a/image.go
+++ b/image.go
@@ -533,7 +533,7 @@ func (i *Image) ColorModel() color.Model {
 // Note that important logic should not rely on At result since
 // At might include a very slight error on some machines.
 //
-// At can't be called before the main loop (ebiten.Run) starts (as of version 1.4.0-alpha).
+// At can't be called outside the main loop (ebiten.Run's updating function) starts (as of version 1.4.0-alpha).
 func (i *Image) At(x, y int) color.Color {
 	if i.isDisposed() {
 		return color.RGBA{}
@@ -550,7 +550,7 @@ func (i *Image) At(x, y int) color.Color {
 //
 // Set loads pixels from GPU to system memory if necessary, which means that Set can be slow.
 //
-// Set can't be called before the main loop (ebiten.Run) starts.
+// Set can't be called outside the main loop (ebiten.Run's updating function) starts.
 //
 // If the image is disposed, Set does nothing.
 func (img *Image) Set(x, y int, clr color.Color) {