diff --git a/default.nix b/default.nix
index ee61fbf..5acaf8f 100644
--- a/default.nix
+++ b/default.nix
@@ -45,6 +45,10 @@ let
     settings.formatter.shfmt.options = [ "--space-redirects" ];
   };
 
+  # The resulting package is built to always use this Nix version, such that the result is reproducible
+  # TODO: Switch this to pkgs.nixVersions.minimum, because that's what Nixpkgs CI should use
+  defaultNixPackage = pkgs.nix;
+
   packages = {
     build = pkgs.callPackage ./package.nix {
       inherit
@@ -54,10 +58,12 @@ let
         testNixpkgsPath
         version
         ;
+      nix = defaultNixPackage;
     };
 
     shell = pkgs.mkShell {
       env.NIX_CHECK_BY_NAME_EXPR_PATH = toString runtimeExprPath;
+      env.NIX_CHECK_BY_NAME_NIX_PACKAGE = lib.getBin defaultNixPackage;
       env.NIX_PATH = "test-nixpkgs=${toString testNixpkgsPath}:test-nixpkgs/lib=${toString nixpkgsLibPath}";
       env.RUST_SRC_PATH = "${pkgs.rustPlatform.rustLibSrc}";
       inputsFrom = [ packages.build ];
@@ -69,6 +75,7 @@ let
         rust-analyzer
         rustfmt
         treefmtEval.config.build.wrapper
+        defaultNixPackage
       ];
     };
 
diff --git a/package.nix b/package.nix
index 479d99b..b539f2e 100644
--- a/package.nix
+++ b/package.nix
@@ -33,6 +33,7 @@ rustPlatform.buildRustPackage {
     makeWrapper
   ];
   env.NIX_CHECK_BY_NAME_EXPR_PATH = "${runtimeExprPath}";
+  env.NIX_CHECK_BY_NAME_NIX_PACKAGE = lib.getBin nix;
   env.NIX_PATH = "test-nixpkgs=${testNixpkgsPath}:test-nixpkgs/lib=${nixpkgsLibPath}";
   preCheck = initNix;
   postCheck = ''
@@ -41,6 +42,7 @@ rustPlatform.buildRustPackage {
   '';
   postInstall = ''
     wrapProgram $out/bin/nixpkgs-check-by-name \
-      --set NIX_CHECK_BY_NAME_EXPR_PATH "$NIX_CHECK_BY_NAME_EXPR_PATH"
+      --set NIX_CHECK_BY_NAME_EXPR_PATH "$NIX_CHECK_BY_NAME_EXPR_PATH" \
+      --set NIX_CHECK_BY_NAME_NIX_PACKAGE ${lib.getBin nix}
   '';
 }
diff --git a/src/eval.rs b/src/eval.rs
index eba7c44..c72546b 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -125,8 +125,12 @@ pub fn check_values(
     let expr_path = std::env::var("NIX_CHECK_BY_NAME_EXPR_PATH")
         .with_context(|| "Could not get environment variable NIX_CHECK_BY_NAME_EXPR_PATH")?;
 
+    // Pinning nix in this way makes the tool more reproducible
+    let nix_package = std::env::var("NIX_CHECK_BY_NAME_NIX_PACKAGE")
+        .with_context(|| "Could not get environment variable NIX_CHECK_BY_NAME_NIX_PACKAGE")?;
+
     // With restrict-eval, only paths in NIX_PATH can be accessed. We explicitly specify them here.
-    let mut command = process::Command::new("nix-instantiate");
+    let mut command = process::Command::new(format!("{nix_package}/bin/nix-instantiate"));
     command
         // Capture stderr so that it can be printed later in case of failure
         .stderr(process::Stdio::piped())