diff --git a/flake.nix b/flake.nix
index 87b00edf4..dd3a25e9e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,7 +23,7 @@
 
       crossSystems = [ "armv6l-linux" "armv7l-linux" ];
 
-      stdenvs = [ "gccStdenv" "clangStdenv" "clang11Stdenv" "stdenv" ];
+      stdenvs = [ "gccStdenv" "clangStdenv" "clang11Stdenv" "stdenv" "libcxxStdenv" ];
 
       forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
       forAllSystemsAndStdenvs = f: forAllSystems (system:
diff --git a/src/libstore/s3.hh b/src/libstore/s3.hh
index 3f55c74db..cdb3e5908 100644
--- a/src/libstore/s3.hh
+++ b/src/libstore/s3.hh
@@ -5,6 +5,7 @@
 #include "ref.hh"
 
 #include <optional>
+#include <string>
 
 namespace Aws { namespace Client { class ClientConfiguration; } }
 namespace Aws { namespace S3 { class S3Client; } }