diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 13bc1b8ea64..0f892f9c320 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -381,11 +381,6 @@ AttrPath AttrCursor::getAttrPath(Symbol name) const
     return attrPath;
 }
 
-std::string toAttrPathStr(EvalState & state, const AttrPath & attrPath)
-{
-    return dropEmptyInitThenConcatStringsSep(".", state.symbols.resolve(attrPath));
-}
-
 std::string AttrCursor::getAttrPathStr() const
 {
     return getAttrPath().to_string(root->state);
diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index 5f7b8ab2e6d..f21313a1040 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -709,6 +709,7 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
                 keyDecoded = base64::decode(k.key);
             } catch (Error & e) {
                 e.addTrace({}, "while decoding public key '%s' used for git signature", k.key);
+                throw;
             }
             auto fingerprint =
                 trim(hashString(HashAlgorithm::SHA256, keyDecoded).to_string(nix::HashFormat::Base64, false), "=");
@@ -1121,6 +1122,13 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
     {
     }
 
+    ~GitFileSystemObjectSinkImpl()
+    {
+        // Make sure the worker threads are destroyed before any state
+        // they're referring to.
+        workers.shutdown();
+    }
+
     struct Child;
 
     /// A directory to be written as a Git tree.
diff --git a/src/libstore/build-result.cc b/src/libstore/build-result.cc
index c9ac7d60b7e..4967b64423d 100644
--- a/src/libstore/build-result.cc
+++ b/src/libstore/build-result.cc
@@ -2,8 +2,6 @@
 #include "nix/util/json-utils.hh"
 #include <array>
 
-#include <nlohmann/json.hpp>
-
 namespace nix {
 
 bool BuildResult::operator==(const BuildResult &) const noexcept = default;
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index e3d4bb4a8a2..ea71ffff5dc 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -19,8 +19,6 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 
-#include <nlohmann/json.hpp>
-
 #include <sodium.h>
 
 namespace nix {
@@ -513,14 +511,6 @@ std::string_view printHashAlgo(HashAlgorithm ha)
     }
 }
 
-void to_json(nlohmann::json & json, const Hash & hash)
-{
-    json = nlohmann::json::object({
-        {"algo", printHashAlgo(hash.algo)},
-        {"base16", hash.to_string(HashFormat::Base16, false)},
-    });
-}
-
 } // namespace nix
 
 namespace nlohmann {
diff --git a/src/libutil/include/nix/util/hash.hh b/src/libutil/include/nix/util/hash.hh
index 427d49a42b7..54b7051055f 100644
--- a/src/libutil/include/nix/util/hash.hh
+++ b/src/libutil/include/nix/util/hash.hh
@@ -7,8 +7,6 @@
 #include "nix/util/file-system.hh"
 #include "nix/util/json-impls.hh"
 
-#include <nlohmann/json_fwd.hpp>
-
 namespace nix {
 
 MakeError(BadHash, Error);
@@ -216,11 +214,6 @@ parseHashAlgoOpt(std::string_view s, const ExperimentalFeatureSettings & xpSetti
  */
 std::string_view printHashAlgo(HashAlgorithm ha);
 
-/**
- * Write a JSON serialisation of the format `{"algo":"<sha1|...>","base16":"<hex>"}`.
- */
-void to_json(nlohmann::json & json, const Hash & hash);
-
 struct AbstractHashSink : virtual Sink
 {
     virtual HashResult finish() = 0;
diff --git a/src/libutil/include/nix/util/thread-pool.hh b/src/libutil/include/nix/util/thread-pool.hh
index 6080ec6098a..63f1141f6a5 100644
--- a/src/libutil/include/nix/util/thread-pool.hh
+++ b/src/libutil/include/nix/util/thread-pool.hh
@@ -52,6 +52,12 @@ public:
      */
     void process();
 
+    /**
+     * Shut down all worker threads and wait until they've exited.
+     * Active work items are finished, but any pending work items are discarded.
+     */
+    void shutdown();
+
 private:
 
     size_t maxThreads;
@@ -72,8 +78,6 @@ private:
     std::condition_variable work;
 
     void doWork(bool mainThread);
-
-    void shutdown();
 };
 
 /**