diff --git a/lix/libstore/build/local-derivation-goal.cc b/lix/libstore/build/local-derivation-goal.cc
index 48868105e..d1e1f2cfb 100644
--- a/lix/libstore/build/local-derivation-goal.cc
+++ b/lix/libstore/build/local-derivation-goal.cc
@@ -14,7 +14,7 @@
 #include "lix/libstore/daemon.hh"
 #include "lix/libutil/result.hh"
 #include "lix/libutil/topo-sort.hh"
-#include "lix/libutil/json-utils.hh"
+#include "lix/libutil/json.hh"
 #include "lix/libutil/cgroup.hh"
 #include "lix/libstore/build/personality.hh"
 #include "lix/libutil/namespaces.hh"
diff --git a/lix/libstore/derivations.cc b/lix/libstore/derivations.cc
index 8ab203519..9553117cb 100644
--- a/lix/libstore/derivations.cc
+++ b/lix/libstore/derivations.cc
@@ -7,7 +7,6 @@
 #include "lix/libutil/types.hh"
 #include "lix/libstore/common-protocol.hh"
 #include "lix/libstore/common-protocol-impl.hh"
-#include "lix/libutil/json-utils.hh"
 #include "lix/libutil/strings.hh"
 #include "lix/libutil/backed-string-view.hh"
 
diff --git a/lix/libutil/abstract-setting-to-json.hh b/lix/libutil/abstract-setting-to-json.hh
index 9a0ba0532..f8f8c9636 100644
--- a/lix/libutil/abstract-setting-to-json.hh
+++ b/lix/libutil/abstract-setting-to-json.hh
@@ -2,7 +2,6 @@
 ///@file
 
 #include "lix/libutil/config.hh"
-#include "lix/libutil/json-utils.hh"
 // Required for instances of to_json and from_json for ExperimentalFeature
 #include "lix/libutil/experimental-features-json.hh"
 #include "lix/libutil/json.hh"
diff --git a/lix/libutil/args.cc b/lix/libutil/args.cc
index 573382a5f..cb7eb9662 100644
--- a/lix/libutil/args.cc
+++ b/lix/libutil/args.cc
@@ -2,7 +2,7 @@
 #include "lix/libutil/args/root.hh"
 #include "lix/libutil/hash.hh"
 #include "lix/libutil/strings.hh"
-#include "lix/libutil/json-utils.hh" // IWYU pragma: keep (instances)
+#include "lix/libutil/json.hh" // IWYU pragma: keep (instances)
 #include "lix/libutil/environment-variables.hh"
 
 #include "lix/libutil/experimental-features-json.hh" // IWYU pragma: keep (instances)
diff --git a/lix/libutil/deprecated-features-json.hh b/lix/libutil/deprecated-features-json.hh
index 913c437cd..e99613df0 100644
--- a/lix/libutil/deprecated-features-json.hh
+++ b/lix/libutil/deprecated-features-json.hh
@@ -2,7 +2,7 @@
 ///@file
 
 #include "lix/libutil/deprecated-features.hh"
-#include "lix/libutil/json-utils.hh"
+#include "lix/libutil/json-fwd.hh"
 
 namespace nix {
 
diff --git a/lix/libutil/experimental-features-json.hh b/lix/libutil/experimental-features-json.hh
index 8329c7e41..1f34ccd52 100644
--- a/lix/libutil/experimental-features-json.hh
+++ b/lix/libutil/experimental-features-json.hh
@@ -2,7 +2,7 @@
 ///@file
 
 #include "lix/libutil/experimental-features.hh"
-#include "lix/libutil/json-utils.hh"
+#include "lix/libutil/json-fwd.hh"
 
 namespace nix {
 
diff --git a/lix/libutil/json-utils.cc b/lix/libutil/json-utils.cc
index 5f6d9c6c1..caa11a41e 100644
--- a/lix/libutil/json-utils.cc
+++ b/lix/libutil/json-utils.cc
@@ -1,4 +1,4 @@
-#include "lix/libutil/json-utils.hh"
+#include "lix/libutil/json.hh"
 #include "lix/libutil/error.hh"
 
 namespace nix {
diff --git a/lix/libutil/json-utils.hh b/lix/libutil/json-utils.hh
deleted file mode 100644
index 9a955d9c6..000000000
--- a/lix/libutil/json-utils.hh
+++ /dev/null
@@ -1,42 +0,0 @@
-#pragma once
-///@file
-
-#include "lix/libutil/json.hh"
-
-/**
- * This "instance" is widely requested, see
- * https://github.com/nlohmann/json/issues/1749, but momentum has stalled
- * out. Writing there here in Nix as a stop-gap.
- *
- * We need to make sure the underlying type does not use `null` for this to
- * round trip. We do that with a static assert.
- */
-template<typename T>
-struct nix::json::adl_serializer<std::optional<T>> {
-    /**
-     * @brief Convert a JSON type to an `optional<T>` treating
-     *        `null` as `std::nullopt`.
-     */
-    static void from_json(const auto & json, std::optional<T> & t) {
-        static_assert(
-            nix::json::avoids_null<T>::value,
-            "null is already in use for underlying type's JSON");
-        t = json.is_null()
-            ? std::nullopt
-            : std::make_optional(json.template get<T>());
-    }
-
-    /**
-     *  @brief Convert an optional type to a JSON type  treating `std::nullopt`
-     *         as `null`.
-     */
-    static void to_json(auto & json, const std::optional<T> & t) {
-        static_assert(
-            nix::json::avoids_null<T>::value,
-            "null is already in use for underlying type's JSON");
-        if (t)
-            json = *t;
-        else
-            json = nullptr;
-    }
-};
diff --git a/lix/libutil/json.hh b/lix/libutil/json.hh
index 9ecee6e20..03e452b38 100644
--- a/lix/libutil/json.hh
+++ b/lix/libutil/json.hh
@@ -105,6 +105,34 @@ struct adl_serializer<T, void>
         return T::from_json(std::forward<Json>(j));
     }
 };
+
+template<typename T>
+struct adl_serializer<std::optional<T>>
+{
+    /**
+     * @brief Convert a JSON type to an `optional<T>` treating
+     *        `null` as `std::nullopt`.
+     */
+    static void from_json(const auto & json, std::optional<T> & t)
+    {
+        static_assert(avoids_null<T>::value, "null is already in use for underlying type's JSON");
+        t = json.is_null() ? std::nullopt : std::make_optional(json.template get<T>());
+    }
+
+    /**
+     *  @brief Convert an optional type to a JSON type  treating `std::nullopt`
+     *         as `null`.
+     */
+    static void to_json(auto & json, const std::optional<T> & t)
+    {
+        static_assert(avoids_null<T>::value, "null is already in use for underlying type's JSON");
+        if (t) {
+            json = *t;
+        } else {
+            json = nullptr;
+        }
+    }
+};
 }
 
 }
diff --git a/lix/libutil/meson.build b/lix/libutil/meson.build
index 63ce56905..7a93b4981 100644
--- a/lix/libutil/meson.build
+++ b/lix/libutil/meson.build
@@ -95,7 +95,6 @@ libutil_headers = files(
   'input-accessor.hh',
   'json.hh',
   'json-fwd.hh',
-  'json-utils.hh',
   'logging.hh',
   'logging-json.hh',
   'lru-cache.hh',
diff --git a/tests/unit/libutil/json-utils.cc b/tests/unit/libutil/json-utils.cc
index 77cd56034..a08137312 100644
--- a/tests/unit/libutil/json-utils.cc
+++ b/tests/unit/libutil/json-utils.cc
@@ -3,7 +3,7 @@
 
 #include <gtest/gtest.h>
 
-#include "lix/libutil/json-utils.hh"
+#include "lix/libutil/json.hh"
 
 namespace nix {