diff --git a/pkgs/pkgs-lib/formats.nix b/pkgs/pkgs-lib/formats.nix
index 879b233bb670..2f3e5ad9d191 100644
--- a/pkgs/pkgs-lib/formats.nix
+++ b/pkgs/pkgs-lib/formats.nix
@@ -472,14 +472,12 @@ optionalAttrs allowAliases aliases
           runCommand name
             {
               nativeBuildInputs = [ json2x ];
-              value = builtins.toJSON value;
+              inherit value;
               preferLocalBuild = true;
               __structuredAttrs = true;
             }
             ''
-              valuePath="$TMPDIR/value"
-              printf "%s" "$value" > "$valuePath"
-              json2x toml "$valuePath" "$out"
+              json2x toml --unwrap value "$NIX_ATTRS_JSON_FILE" "$out"
             ''
         ) { };
 
diff --git a/pkgs/pkgs-lib/formats/json2x/src/main.rs b/pkgs/pkgs-lib/formats/json2x/src/main.rs
index b9025c67f42a..1464fb8972b9 100644
--- a/pkgs/pkgs-lib/formats/json2x/src/main.rs
+++ b/pkgs/pkgs-lib/formats/json2x/src/main.rs
@@ -10,6 +10,9 @@ use argh::{FromArgValue, FromArgs};
 /// Convert a JSON file to another format
 #[derive(FromArgs)]
 struct Args {
+    /// convert only value of this attribute
+    #[argh(option)]
+    unwrap: Option<String>,
     /// format of the output file, possible values: toml
     #[argh(positional)]
     format: Format,
@@ -29,16 +32,31 @@ enum Format {
 fn main() -> anyhow::Result<()> {
     let args: Args = argh::from_env();
 
-    let input = read_to_string(&args.input)
+    let json_text = read_to_string(&args.input)
         .with_context(|| format!("failed to read {}", args.input.display()))?;
-    let input: serde_json::Value = serde_json::from_str(&input)
+    let parsed_json: serde_json::Value = serde_json::from_str(&json_text)
         .with_context(|| format!("failed to parse {}", args.input.display()))?;
+    let output_value = if let Some(unwrap_key) = args.unwrap {
+        parsed_json
+            .as_object()
+            .ok_or_else(|| anyhow::anyhow!("{} does not contain an object", args.input.display()))?
+            .get(&unwrap_key)
+            .ok_or_else(|| {
+                anyhow::anyhow!(
+                    "{} does not containt attribute '{unwrap_key}'",
+                    args.input.display()
+                )
+            })?
+    } else {
+        &parsed_json
+    };
     let mut output = File::create(&args.output)
         .with_context(|| format!("failed to create {}", args.output.display()))?;
 
     match args.format {
         Format::Toml => {
-            let content = toml::to_string(&input).context("failed to serialize value to toml")?;
+            let content =
+                toml::to_string(output_value).context("failed to serialize value to toml")?;
             output
                 .write_all(content.as_bytes())
                 .with_context(|| format!("failed to write to {}", args.output.display()))?;