diff --git a/default.nix b/default.nix
index 4565454..f93187b 100644
--- a/default.nix
+++ b/default.nix
@@ -74,6 +74,7 @@ let
   });
 in pkgs.python3Packages.buildPythonPackage rec {
   pname = "tockloader";
+  pyproject = true;
   version = let
       pattern = "^__version__ = ['\"]([^'\"]*)['\"]\n";
     in elemAt (match pattern (readFile ./tockloader/_version.py)) 0;
@@ -90,6 +91,7 @@ in pkgs.python3Packages.buildPythonPackage rec {
     pycrypto
     siphash
     ecdsa
+    flit-core
   ] ++ (lib.optional withUnfreePkgs pynrfjprog);
 
   src = ./.;
@@ -98,8 +100,7 @@ in pkgs.python3Packages.buildPythonPackage rec {
   doCheck = withUnfreePkgs;
 
   # Make other dependencies explicitly available as passthru attributes
-  passthru = {
-    inherit nrf-command-line-tools;
-    pynrfjprog = python3Packages.pynrfjprog;
-  };
+  passthru = if withUnfreePkgs then {
+      inherit pynrfjprog nrf-command-line-tools;
+    } else { };
 }
diff --git a/pyproject.toml b/pyproject.toml
index 8fe704d..e25b1ac 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -16,7 +16,6 @@ dependencies = [
     "crcmod >= 1.7",
     "ecdsa >= 0.19.1",
     "pycryptodome >= 3.15.0",
-    "pynrfjprog == 10.19.0",
     "pyserial >= 3.0.1",
     "siphash >= 0.0.1",
     "six >= 1.9.0",
@@ -24,6 +23,9 @@ dependencies = [
     "tqdm >= 4.45.0 ",
     "questionary >= 1.10.0",
 ]
+optional-delendencies = [
+    "pynrfjprog == 10.22.1",
+]
 
 [project.urls]
 Home = "https://github.com/tock/tockloader"
diff --git a/requirements.txt b/requirements.txt
index 783780d..aab07d4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ colorama==0.4.6
 crcmod==1.7
 ecdsa==0.19.1
 pycryptodome==3.22.0
-pynrfjprog==10.19.0
+pynrfjprog==10.22.1
 pyserial==3.5
 questionary==2.1.0
 setuptools==78.1.1