diff --git a/packages/bubblewrap/default.nix b/packages/bubblewrap/default.nix
index 1538d00..1e5db14 100644
--- a/packages/bubblewrap/default.nix
+++ b/packages/bubblewrap/default.nix
@@ -27,6 +27,10 @@ stdenv.mkDerivation rec {
       --replace "/var/tmp" "$TMPDIR"
   '';
 
+  # GCC 15 (nixpkgs 26.05) defaults to -std=gnu23, where `bool`/`true`/`false`
+  # are keywords; this old bubblewrap fork still does `typedef int bool;`.
+  env.NIX_CFLAGS_COMPILE = "-std=gnu17";
+
   nativeBuildInputs = [
     docbook_xsl
     libxslt