diff --git a/tools/build/checkstyle9.pl b/tools/build/checkstyle9.pl
index 24e33712ceda..fff6fff533be 100755
--- a/tools/build/checkstyle9.pl
+++ b/tools/build/checkstyle9.pl
@@ -204,6 +204,7 @@ sub help {
 			const|
 			_*restrict|
 			volatile|
+			__capability|
 			QEMU_NORETURN|
 			QEMU_WARN_UNUSED_RESULT|
 			QEMU_SENTINEL|