diff --git a/tools/cmd/at/set_background_opacity.go b/tools/cmd/at/set_background_opacity.go
index 039b49a6e..fa67e8d69 100644
--- a/tools/cmd/at/set_background_opacity.go
+++ b/tools/cmd/at/set_background_opacity.go
@@ -9,11 +9,5 @@ func parse_opacity(arg string) (float64, error) {
 	if err != nil {
 		return 0, nil
 	}
-	if ans < 0.1 {
-		ans = 0.1
-	}
-	if ans > 1 {
-		ans = 1
-	}
-	return ans, nil
+	return max(0, min(ans, 1)), nil
 }