5 files changed, 19 insertions, 10 deletions
diff --git a/third_party/nix/src/libexpr/eval.cc b/third_party/nix/src/libexpr/eval.cc
index 2b825bfd27..0f3b7fabe0 100644
--- a/third_party/nix/src/libexpr/eval.cc
+++ b/third_party/nix/src/libexpr/eval.cc
@@ -5,10 +5,13 @@
 #include <cstring>
 #include <fstream>
 #include <iostream>
+#include <memory>
 #include <new>
 #include <optional>
 #include <variant>
 
+#define GC_INCLUDE_NEW
+
 #include <absl/strings/match.h>
 #include <gc/gc.h>
 #include <gc/gc_cpp.h>
@@ -40,6 +43,10 @@ static char* dupString(const char* s) {
   return t;
 }
 
+std::shared_ptr<Value*> allocRootValue(Value* v) {
+  return std::allocate_shared<Value*>(traceable_allocator<Value*>(), v);
+}
+
 static void printValue(std::ostream& str, std::set<const Value*>& active,
                        const Value& v) {
   checkInterrupt();
diff --git a/third_party/nix/src/libexpr/nixexpr.hh b/third_party/nix/src/libexpr/nixexpr.hh
index 4b2bd86ef9..365235377f 100644
--- a/third_party/nix/src/libexpr/nixexpr.hh
+++ b/third_party/nix/src/libexpr/nixexpr.hh
@@ -3,6 +3,7 @@
 #include <map>
 #include <optional>
 #include <variant>
+
 #include <absl/container/flat_hash_map.h>
 
 #include "libexpr/symbol-table.hh"
diff --git a/third_party/nix/src/libexpr/value.hh b/third_party/nix/src/libexpr/value.hh
index 7308dd3193..cb1b8796cf 100644
--- a/third_party/nix/src/libexpr/value.hh
+++ b/third_party/nix/src/libexpr/value.hh
@@ -247,4 +247,6 @@ typedef std::map<Symbol, Value*, std::less<Symbol>,
                  traceable_allocator<std::pair<const Symbol, Value*>>>
     ValueMap;
 
+std::shared_ptr<Value*> allocRootValue(Value* v);
+
 }  // namespace nix
diff --git a/third_party/nix/src/nix/command.hh b/third_party/nix/src/nix/command.hh
index f7eaeb7216..01c1ed69d6 100644
--- a/third_party/nix/src/nix/command.hh
+++ b/third_party/nix/src/nix/command.hh
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+
 #include "libexpr/common-eval-args.hh"
 #include "libutil/args.hh"
 
@@ -81,7 +82,7 @@ struct SourceExprCommand : virtual Args, StoreCommand, MixEvalArgs {
 
  private:
   std::shared_ptr<EvalState> evalState;
-  std::shared_ptr<Value> vSourceExpr;
+  std::shared_ptr<Value*> vSourceExpr;
 };
 
 enum RealiseMode { Build, NoBuild, DryRun };
diff --git a/third_party/nix/src/nix/installables.cc b/third_party/nix/src/nix/installables.cc
index cc001d37f3..c6cfc4344f 100644
--- a/third_party/nix/src/nix/installables.cc
+++ b/third_party/nix/src/nix/installables.cc
@@ -1,8 +1,6 @@
 #include <regex>
 #include <utility>
 
-#include <gc/gc.h>
-
 #include "libexpr/attr-path.hh"
 #include "libexpr/common-eval-args.hh"
 #include "libexpr/eval-inline.hh"
@@ -26,7 +24,7 @@ SourceExprCommand::SourceExprCommand() {
 
 Value* SourceExprCommand::getSourceExpr(EvalState& state) {
   if (vSourceExpr != nullptr) {
-    return vSourceExpr.get();
+    return *vSourceExpr;
   }
 
   auto sToplevel = state.symbols.Create("_toplevel");
@@ -34,18 +32,18 @@ Value* SourceExprCommand::getSourceExpr(EvalState& state) {
   // Allocate the vSourceExpr Value as uncollectable. Boehm GC doesn't
   // consider the member variable "alive" during execution causing it to be
   // GC'ed in the middle of evaluation.
-  vSourceExpr = std::allocate_shared<Value>(traceable_allocator<Value>());
+  vSourceExpr = allocRootValue(state.allocValue());
 
   if (!file.empty()) {
-    state.evalFile(lookupFileArg(state, file), *vSourceExpr);
+    state.evalFile(lookupFileArg(state, file), **vSourceExpr);
   } else {
     /* Construct the installation source from $NIX_PATH. */
 
     auto searchPath = state.getSearchPath();
 
-    state.mkAttrs(*vSourceExpr, 1024);
+    state.mkAttrs(**vSourceExpr, 1024);
 
-    mkBool(*state.allocAttr(*vSourceExpr, sToplevel), true);
+    mkBool(*state.allocAttr(**vSourceExpr, sToplevel), true);
 
     std::unordered_set<std::string> seen;
 
@@ -61,7 +59,7 @@ Value* SourceExprCommand::getSourceExpr(EvalState& state) {
                   state.getBuiltin("nixPath"));
       Value* v2 = state.allocValue();
       mkApp(*v2, *v1, mkString(*state.allocValue(), name));
-      mkApp(*state.allocAttr(*vSourceExpr, state.symbols.Create(name)),
+      mkApp(*state.allocAttr(**vSourceExpr, state.symbols.Create(name)),
             state.getBuiltin("import"), *v2);
     };
 
@@ -79,7 +77,7 @@ Value* SourceExprCommand::getSourceExpr(EvalState& state) {
     }
   }
 
-  return vSourceExpr.get();
+  return *vSourceExpr;
 }
 
 ref<EvalState> SourceExprCommand::getEvalState() {