diff --git a/doc.go b/doc.go
index 107266931..f64b7fd4c 100644
--- a/doc.go
+++ b/doc.go
@@ -73,6 +73,7 @@
 // `ebitengl` forces to use OpenGL in any environments.
 //
 // `ebitensinglethread` disables Ebiten's thread safety to unlock maximum performance. If you use this you will have
-// to manage threads yourself. Functions like IsKeyPressed will no longer be concurrent-safe with this build tag and
-// must be called from the main thread.
+// to manage threads yourself. Functions like IsKeyPressed will no longer be concurrent-safe with this build tag.
+// They must be called from the main thread or the same goroutine as the given game's callback functions like Update
+// to RunGame.
 package ebiten