diff --git a/buildbot_nix/__init__.py b/buildbot_nix/__init__.py
index b4849f9..e45ceee 100644
--- a/buildbot_nix/__init__.py
+++ b/buildbot_nix/__init__.py
@@ -59,14 +59,17 @@ class NixBuilder:
     publicHostKey: str | None = None
     sshUser: str | None = None
     sshKey: str | None = None
-    systems: list[str] = field(default_factory=lambda: ["-"])
-    supportedFeatures: list[str] = field(default_factory=lambda: ["-"])
-    mandatoryFeatures: list[str] = field(default_factory=lambda: ["-"])
+    systems: list[str] = field(default_factory=lambda: [])
+    supportedFeatures: list[str] = field(default_factory=lambda: [])
+    mandatoryFeatures: list[str] = field(default_factory=lambda: [])
 
     def to_nix_line(self):
+        systems = ["-"] if not self.systems else self.systems
+        supportedFeatures = ["-"] if not self.supportedFeatures else self.supportedFeatures
+        mandatoryFeatures = ["-"] if not self.mandatoryFeatures else self.mandatoryFeatures
         encoded_public_key = base64.b64encode(self.publicHostKey.encode('ascii')).decode('ascii') if self.publicHostKey is not None else "-"
         fullConnection = f"{self.protocol}://{self.sshUser}@{self.hostName}" if self.sshUser is not None else self.hostName
-        return f"{fullConnection} {",".join(self.systems)} {self.sshKey or "-"} {self.maxJobs} {self.speedFactor} {",".join(self.supportedFeatures)} {",".join(self.mandatoryFeatures)} {encoded_public_key}"
+        return f"{fullConnection} {",".join(systems)} {self.sshKey or "-"} {self.maxJobs} {self.speedFactor} {",".join(supportedFeatures)} {",".join(mandatoryFeatures)} {encoded_public_key}"
 
 
 @dataclass
@@ -666,6 +669,20 @@ def nix_build_config(
 ) -> util.BuilderConfig:
     """Builds one nix flake attribute."""
     factory = util.BuildFactory()
+    factory.addStep(
+        steps.ShellCommand(
+            name="Copy the derivation to the local worker store",
+            command=[
+                "nix",
+                "copy",
+                "--derivation",
+                "--to",
+                "../store",
+                util.Interpolate("%(prop:drv_path)s^*")
+            ]
+        )
+    )
+
     factory.addStep(
         NixBuildCommand(
             env={},
@@ -687,6 +704,8 @@ def nix_build_config(
                 "7200",
                 "--builders",
                 builders_spec,
+                "--store",
+                util.Interpolate("%(prop:builddir)s/store"),
                 "--out-link",
                 util.Interpolate("result-%(prop:attr)s"),
                 util.Interpolate("%(prop:drv_path)s^*"),
@@ -706,6 +725,8 @@ def nix_build_config(
                     "nix",
                     "store",
                     "sign",
+                    "--store",
+                    util.Interpolate("%(prop:builddir)s/store"),
                     "--key-file",
                     signing_keyfile,
                     util.Interpolate(