diff --git a/pkgs/clan-cli/clan_cli/config/__init__.py b/pkgs/clan-cli/clan_cli/config/__init__.py
index f73a9dc..d81fbc2 100644
--- a/pkgs/clan-cli/clan_cli/config/__init__.py
+++ b/pkgs/clan-cli/clan_cli/config/__init__.py
@@ -100,7 +100,6 @@ def options_for_machine(machine_name: str, flake: Optional[Path] = None) -> dict
     proc = subprocess.run(
         nix_eval(
             flags=[
-                "--json",
                 "--show-trace",
                 "--impure",
                 "--expr",
@@ -138,7 +137,6 @@ def read_machine_option_value(machine_name: str, option: str) -> str:
     proc = subprocess.run(
         nix_eval(
             flags=[
-                "--json",
                 "--show-trace",
                 "--extra-experimental-features",
                 "nix-command flakes",
diff --git a/pkgs/clan-cli/clan_cli/config/machine.py b/pkgs/clan-cli/clan_cli/config/machine.py
index 0dec9c1..1e3b29a 100644
--- a/pkgs/clan-cli/clan_cli/config/machine.py
+++ b/pkgs/clan-cli/clan_cli/config/machine.py
@@ -45,7 +45,6 @@ def schema_for_machine(machine_name: str, flake: Optional[Path] = None) -> dict:
     proc = subprocess.run(
         nix_eval(
             flags=[
-                "--json",
                 "--impure",
                 "--show-trace",
                 "--extra-experimental-features",
diff --git a/pkgs/clan-cli/clan_cli/nix.py b/pkgs/clan-cli/clan_cli/nix.py
index 7a29f02..559b823 100644
--- a/pkgs/clan-cli/clan_cli/nix.py
+++ b/pkgs/clan-cli/clan_cli/nix.py
@@ -41,29 +41,30 @@ def nix_build_machine(
 
 
 def nix_eval(flags: list[str]) -> list[str]:
-    if os.environ.get("IN_NIX_SANDBOX"):
-        with tempfile.TemporaryDirectory() as nix_store:
-            return [
-                "nix",
-                "eval",
-                "--show-trace",
-                "--extra-experimental-features",
-                "nix-command flakes",
-                "--override-input",
-                "nixpkgs",
-                str(nixpkgs_source()),
-                # --store is required to prevent this error:
-                # error: cannot unlink '/nix/store/6xg259477c90a229xwmb53pdfkn6ig3g-default-builder.sh': Operation not permitted
-                "--store",
-                nix_store,
-            ] + flags
-    return [
+    default_flags = [
         "nix",
         "eval",
         "--show-trace",
+        "--json",
         "--extra-experimental-features",
         "nix-command flakes",
-    ] + flags
+    ]
+    if os.environ.get("IN_NIX_SANDBOX"):
+        with tempfile.TemporaryDirectory() as nix_store:
+            return (
+                default_flags
+                + [
+                    "--override-input",
+                    "nixpkgs",
+                    str(nixpkgs_source()),
+                    # --store is required to prevent this error:
+                    # error: cannot unlink '/nix/store/6xg259477c90a229xwmb53pdfkn6ig3g-default-builder.sh': Operation not permitted
+                    "--store",
+                    nix_store,
+                ]
+                + flags
+            )
+    return default_flags + flags
 
 
 def nix_shell(packages: list[str], cmd: list[str]) -> list[str]: