diff --git a/WORKSPACE b/WORKSPACE
index a2d575006..87bf2058e 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -136,7 +136,16 @@ nixpkgs_package(
 
 nixpkgs_cc_configure(repository = "@remote_nixpkgs")
 
-nixpkgs_python_configure(repository = "@remote_nixpkgs")
+nixpkgs_python_configure(
+    python2_attribute_path = "python2",
+    repository = "@remote_nixpkgs",
+)
+
+nixpkgs_package(
+    name = "nixpkgs_python_configure_test",
+    nix_file = "//tests:python-test.nix",
+    repository = "@remote_nixpkgs",
+)
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
diff --git a/nixpkgs/nixpkgs.bzl b/nixpkgs/nixpkgs.bzl
index 263bb37c1..96d9b950c 100644
--- a/nixpkgs/nixpkgs.bzl
+++ b/nixpkgs/nixpkgs.bzl
@@ -162,10 +162,12 @@ def _nixpkgs_package_impl(repository_ctx):
 
         # ensure that the output is a directory
         test_path = repository_ctx.which("test")
-        _execute_or_fail(repository_ctx, [test_path, "-d", output_path],
-                         failure_message = "nixpkgs_package '@{}' outputs a single file which is not supported by rules_nixpkgs. Please only use directories.".format(
-                             repository_ctx.name
-                         ),
+        _execute_or_fail(
+            repository_ctx,
+            [test_path, "-d", output_path],
+            failure_message = "nixpkgs_package '@{}' outputs a single file which is not supported by rules_nixpkgs. Please only use directories.".format(
+                repository_ctx.name,
+            ),
         )
 
         # Build a forest of symlinks (like new_local_package() does) to the
@@ -357,14 +359,27 @@ _nixpkgs_python_toolchain = repository_rule(
     },
 )
 
-_python_build_file_content = """
-py_runtime(
-    name = "runtime",
-    files = glob(["**"]),
-    interpreter = "{bin_path}",
-    python_version = "{version}",
-    visibility = ["//visibility:public"],
-)
+_python_nix_file_content = """
+with import <nixpkgs> {{ config = {{}}; overlays = []; }};
+runCommand "bazel-nixpkgs-python-toolchain"
+  {{ executable = false;
+    # Pointless to do this on a remote machine.
+    preferLocalBuild = true;
+    allowSubstitutes = false;
+  }}
+  ''
+    n=$out/BUILD.bazel
+    mkdir -p "$(dirname "$n")"
+
+    cat >>$n <<EOF
+    py_runtime(
+        name = "runtime",
+        interpreter_path = "${{{attribute_path}}}/{bin_path}",
+        python_version = "{version}",
+        visibility = ["//visibility:public"],
+    )
+    EOF
+  ''
 """
 
 def nixpkgs_python_configure(
@@ -375,8 +390,6 @@ def nixpkgs_python_configure(
         python3_bin_path = "bin/python",
         repository = None,
         repositories = {},
-        nix_file = None,
-        nix_file_content = None,
         nix_file_deps = None,
         nixopts = [],
         fail_not_supported = True):
@@ -402,8 +415,6 @@ def nixpkgs_python_configure(
     kwargs = dict(
         repository = repository,
         repositories = repositories,
-        nix_file = nix_file,
-        nix_file_content = nix_file_content,
         nix_file_deps = nix_file_deps,
         nixopts = nixopts,
         fail_not_supported = fail_not_supported,
@@ -413,8 +424,8 @@ def nixpkgs_python_configure(
         python2_runtime = "@%s_python2//:runtime" % name
         nixpkgs_package(
             name = name + "_python2",
-            attribute_path = python2_attribute_path,
-            build_file_content = _python_build_file_content.format(
+            nix_file_content = _python_nix_file_content.format(
+                attribute_path = python2_attribute_path,
                 bin_path = python2_bin_path,
                 version = "PY2",
             ),
@@ -425,8 +436,8 @@ def nixpkgs_python_configure(
         python3_runtime = "@%s_python3//:runtime" % name
         nixpkgs_package(
             name = name + "_python3",
-            attribute_path = python3_attribute_path,
-            build_file_content = _python_build_file_content.format(
+            nix_file_content = _python_nix_file_content.format(
+                attribute_path = python3_attribute_path,
                 bin_path = python3_bin_path,
                 version = "PY3",
             ),
@@ -596,7 +607,7 @@ def _find_children(repository_ctx, target_dir):
         "-print0",
     ]
     exec_result = _execute_or_fail(repository_ctx, find_args)
-    return exec_result.stdout.rstrip("\0").split("\0")
+    return exec_result.stdout.rstrip("\000").split("\000")
 
 def _executable_path(repository_ctx, exe_name, extra_msg = ""):
     """Try to find the executable, fail with an error."""
diff --git a/tests/BUILD.bazel b/tests/BUILD.bazel
index 0ef7f438c..5cc1a5f61 100644
--- a/tests/BUILD.bazel
+++ b/tests/BUILD.bazel
@@ -59,11 +59,12 @@ cc_binary(
 )
 
 # Test nixpkgs_python_configure() by running some Python code.
-py_test(
+test_suite(
     name = "python-test",
-    srcs = ["python-test.py"],
-    python_version = "PY3",
-    srcs_version = "PY3",
+    tests = [
+        "@nixpkgs_python_configure_test//:python2-test",
+        "@nixpkgs_python_configure_test//:python3-test",
+    ],
 )
 
 # Test nixpkgs_sh_posix_configure() checking that Unix commands are in Nix store.
diff --git a/tests/python-test.nix b/tests/python-test.nix
new file mode 100644
index 000000000..8e953a43f
--- /dev/null
+++ b/tests/python-test.nix
@@ -0,0 +1,48 @@
+with import <nixpkgs> { config = {}; overlays = []; };
+runCommand "test-nixpkgs-python-toolchain"
+  { executable = false; }
+  ''
+    mkdir -p $out
+
+    cat >$out/BUILD.bazel <<'EOF_BUILD'
+    py_test(
+        name = "python2-test",
+        main = "python-test.py",
+        srcs = ["python-test.py"],
+        python_version = "PY2",
+        srcs_version = "PY2",
+        visibility = ["//visibility:public"],
+    )
+    py_test(
+        name = "python3-test",
+        main = "python-test.py",
+        srcs = ["python-test.py"],
+        python_version = "PY3",
+        srcs_version = "PY3",
+        visibility = ["//visibility:public"],
+    )
+    EOF_BUILD
+
+    cat >$out/python-test.py <<'EOF_PYTHON'
+    import os
+    import sys
+
+    _failure_message = """\
+    Python interpreter is not provided by the toolchain.
+    Expected: '{expected}'
+    Actual:   '{actual}'.
+    """
+
+    if __name__ == "__main__":
+        if sys.version_info.major == 2:
+            python_bin = "${python2}/bin/python"
+        else:
+            python_bin = "${python3}/bin/python"
+        if not sys.executable == python_bin:
+            sys.stderr.write(_failure_message.format(
+                expected = python_bin,
+                actual = sys.executable,
+            ))
+            sys.exit(1)
+    EOF_PYTHON
+  ''
diff --git a/tests/python-test.py b/tests/python-test.py
deleted file mode 100644
index 5cb28d610..000000000
--- a/tests/python-test.py
+++ /dev/null
@@ -1,19 +0,0 @@
-import os
-import sys
-
-_failure_message = """\
-Python interpreter is not provided by the toolchain.
-Expected: '{expected}'
-Actual:   '{actual}'.
-"""
-
-if __name__ == "__main__":
-    runfiles_dir = os.environ["RUNFILES_DIR"]
-    python_bin = os.path.join(
-        runfiles_dir, "nixpkgs_python_toolchain_python3", "bin", "python")
-    if not sys.executable == python_bin:
-        print(_failure_message.format(
-            expected = python_bin,
-            actual = sys.executable,
-        ), file=sys.stderr)
-        sys.exit(1)