diff --git a/util/nixshell/toolchain.nix b/util/nixshell/toolchain.nix
index da252f268a..08b55980e1 100644
--- a/util/nixshell/toolchain.nix
+++ b/util/nixshell/toolchain.nix
@@ -8,7 +8,7 @@ stdenvNoCC.mkDerivation {
 		curl
 		flex
 		git
-		gnat11
+		gnat12
 		gnumake
 		patch
 		zlib