diff --git a/third_party/nix/src/libstore/build.cc b/third_party/nix/src/libstore/build.cc
index afd2374b0..27d6aa611 100644
--- a/third_party/nix/src/libstore/build.cc
+++ b/third_party/nix/src/libstore/build.cc
@@ -713,7 +713,7 @@ HookInstance::~HookInstance() {
 
 //////////////////////////////////////////////////////////////////////
 
-typedef std::map<std::string, std::string> StringRewrites;
+using StringRewrites = std::map<std::string, std::string>;
 
 std::string rewriteStrings(std::string s, const StringRewrites& rewrites) {
   for (auto& i : rewrites) {
diff --git a/third_party/nix/src/libstore/derivations.hh b/third_party/nix/src/libstore/derivations.hh
index 63527149d..dfdebdd01 100644
--- a/third_party/nix/src/libstore/derivations.hh
+++ b/third_party/nix/src/libstore/derivations.hh
@@ -42,10 +42,8 @@ using DerivationOutputs = absl::btree_map<std::string, DerivationOutput>;
 
 /* For inputs that are sub-derivations, we specify exactly which
    output IDs we are interested in. */
-// TODO(grfn): change to absl::flat_hash_map
-using DerivationInputs = std::map<Path, StringSet>;
+using DerivationInputs = absl::btree_map<Path, StringSet>;
 
-// TODO(grfn): change to absl::flat_hash_map
 using StringPairs = std::map<std::string, std::string>;
 
 struct BasicDerivation {