diff --git a/pynixify/base.py b/pynixify/base.py
index 39eee63..6999e58 100644
--- a/pynixify/base.py
+++ b/pynixify/base.py
@@ -37,7 +37,7 @@ async def source(self, extra_args=[]) -> Path:
     def attr(self) -> str:
         raise NotImplementedError()
 
-    async def metadata(self) -> PackageMetadata:
+    async def metadata(self, interpreter) -> PackageMetadata:
         from pynixify.package_requirements import run_nix_build, NixBuildError
         source = await self.source()
         if source.name.endswith('.whl'):
@@ -56,7 +56,10 @@ async def metadata(self) -> PackageMetadata:
             '--no-build-output',
             '--arg',
             'file',
-            str(source.resolve())
+            str(source.resolve()),
+            '--arg',
+            'python',
+            "(import <nixpkgs> { }).%s" % interpreter
         )
         if (nix_store_path / 'failed').exists():
             print(f'Error parsing metadata of {source}. Assuming it has no metadata.')
diff --git a/pynixify/command.py b/pynixify/command.py
index 6b9959a..fcb5970 100644
--- a/pynixify/command.py
+++ b/pynixify/command.py
@@ -153,6 +153,15 @@ def main():
             "executed by pynixify. If it isn't specified, it will be set to "
             "the number of CPUs in the system."
         ))
+    parser.add_argument(
+        "-p",
+        "--py",
+        default="python3",
+        help=(
+            "Name of the nixpkgs python interpreter package to install in the "
+            "generated shell.nix. Defaults to 'python3'."
+        ),
+    )
     args = parser.parse_args()
 
     asyncio.run(_main_async(
@@ -166,6 +175,7 @@ def main():
         ignore_test_requirements_for=args.ignore_tests.split(',') if args.ignore_tests else [],
         max_jobs=args.max_jobs,
         generate_only_overlay=args.overlay_only,
+        interpreter=args.py,
     ))
 
 async def _main_async(
@@ -178,7 +188,8 @@ async def _main_async(
         ignore_test_requirements_for: List[str],
         load_all_test_requirements: bool,
         max_jobs: Optional[int],
-        generate_only_overlay:bool):
+        generate_only_overlay: bool,
+        interpreter: str):
 
     if nixpkgs is not None:
         pynixify.nixpkgs_sources.NIXPKGS_URL = nixpkgs
@@ -203,7 +214,7 @@ async def _main_async(
         all_requirements.append(Requirement(req_))
 
     await asyncio.gather(*(
-        version_chooser.require(req)
+        version_chooser.require(req, interpreter)
         for req in all_requirements
     ))
 
@@ -218,13 +229,13 @@ async def _main_async(
     async def write_package_expression(package: PyPIPackage):
         reqs: ChosenPackageRequirements
         reqs = ChosenPackageRequirements.from_package_requirements(
-            await evaluate_package_requirements(package),
+            await evaluate_package_requirements(package, extra_args=[interpreter]),
             version_chooser=version_chooser,
             load_tests=version_chooser.should_load_tests(package.pypi_name),
         )
 
         sha256 = await get_path_hash(await package.source())
-        meta = await package.metadata()
+        meta = await package.metadata(interpreter)
         version = await load_nixpkgs_version()
         try:
             (pname, ext) = await get_pypi_data(
@@ -277,7 +288,7 @@ async def write_package_expression(package: PyPIPackage):
         packages.append(p)
 
     with (base_path / 'shell.nix').open('w') as fp:
-        expr = build_shell_nix_expression(packages)
+        expr = build_shell_nix_expression(packages, interpreter)
         fp.write(await nixfmt(expr))
 
 
diff --git a/pynixify/data/parse_setuppy_data.nix b/pynixify/data/parse_setuppy_data.nix
index 7ffbe22..0a06e76 100644
--- a/pynixify/data/parse_setuppy_data.nix
+++ b/pynixify/data/parse_setuppy_data.nix
@@ -1,5 +1,6 @@
-{ file, stdenv ? (import <nixpkgs> { }).stdenv, lib ? (import <nixpkgs> { }).lib
-, unzip ? (import <nixpkgs> { }).unzip, python ? (import <nixpkgs> { }).python3
+{ file, python, stdenv ? (import <nixpkgs> { }).stdenv, lib ? (import <nixpkgs> { }).lib
+, unzip ? (import <nixpkgs> { }).unzip, git ? (import <nixpkgs> { }).git
+, fetchFromGitLab ? (import <nixpkgs> { }).fetchFromGitLab
 }:
 
 let
diff --git a/pynixify/expression_builder.py b/pynixify/expression_builder.py
index 11c20a6..dd52537 100644
--- a/pynixify/expression_builder.py
+++ b/pynixify/expression_builder.py
@@ -123,7 +123,7 @@
 """)
 
 shell_nix_template = Template("""${DISCLAIMER}
-    { python ? "python3" }:
+    { python ? ${interpreter | nix} }:
     let
         pkgs = import ./nixpkgs.nix {};
         pythonPkg = builtins.getAttr python pkgs;
@@ -206,8 +206,8 @@ def build_overlayed_nixpkgs(
     return overlayed_nixpkgs_template.render(DISCLAIMER=DISCLAIMER, **locals())
 
 
-def build_shell_nix_expression(packages: List[Package]) -> str:
-    return shell_nix_template.render(DISCLAIMER=DISCLAIMER, packages=packages)
+def build_shell_nix_expression(packages: List[Package], interpreter: str) -> str:
+    return shell_nix_template.render(DISCLAIMER=DISCLAIMER, packages=packages, interpreter=interpreter, nix=escape_string)
 
 
 async def nixfmt(expr: str) -> str:
diff --git a/pynixify/package_requirements.py b/pynixify/package_requirements.py
index 5a17cc5..5a8e4ce 100644
--- a/pynixify/package_requirements.py
+++ b/pynixify/package_requirements.py
@@ -45,7 +45,7 @@ def from_result_path(cls, result_path: Path):
         return cls(**kwargs)
 
 
-async def eval_path_requirements(path: Path) -> PackageRequirements:
+async def eval_path_requirements(path: Path, interpreter: str) -> PackageRequirements:
     nix_expression_path = Path(__file__).parent / "data" / "parse_setuppy_data.nix"
     if path.name.endswith('.whl'):
         # Some nixpkgs packages use a wheel as source, which don't have a
@@ -64,7 +64,10 @@ async def eval_path_requirements(path: Path) -> PackageRequirements:
         '--no-build-output',
         '--arg',
         'file',
-        str(path.resolve())
+        str(path.resolve()),
+        '--arg',
+        'python',
+        "(import <nixpkgs> { }).%s" % interpreter
     )
     if (nix_store_path / 'failed').exists():
         print(f'Error parsing requirements of {path}. Assuming it has no dependencies.')
diff --git a/pynixify/version_chooser.py b/pynixify/version_chooser.py
index debe2ee..7dd2f12 100644
--- a/pynixify/version_chooser.py
+++ b/pynixify/version_chooser.py
@@ -46,7 +46,7 @@ def __init__(self, nixpkgs_data: NixpkgsData, pypi_data: PyPIData,
         self.evaluate_requirements = req_evaluate
         self.should_load_tests = should_load_tests
 
-    async def require(self, r: Requirement, coming_from: Optional[Package]=None):
+    async def require(self, r: Requirement, interpreter: str, coming_from: Optional[Package]=None):
         pkg: Package
 
         if r.marker and not r.marker.evaluate():
@@ -119,14 +119,14 @@ async def require(self, r: Requirement, coming_from: Optional[Package]=None):
 
             pkg = max(pkgs, key=operator.attrgetter('version'))
         self._choosed_packages[canonicalize_name(r.name)] = (pkg, r.specifier)
-        reqs: PackageRequirements = await self.evaluate_requirements(pkg)
+        reqs: PackageRequirements = await self.evaluate_requirements(pkg, extra_args=[interpreter])
 
         if isinstance(pkg, NixPackage) or (
                 not self.should_load_tests(canonicalize_name(r.name))):
             reqs.test_requirements = []
 
         await asyncio.gather(*(
-            self.require(req, coming_from=pkg)
+            self.require(req, interpreter, coming_from=pkg)
             for req in (reqs.runtime_requirements + reqs.test_requirements +
                         reqs.build_requirements)
         ))
@@ -160,8 +160,9 @@ def all_pypi_packages(self) -> List[PyPIPackage]:
 
 async def evaluate_package_requirements(
         pkg: Package, extra_args=[]) -> PackageRequirements:
+    interpreter = extra_args.pop()
     src = await pkg.source(extra_args)
-    return await eval_path_requirements(src)
+    return await eval_path_requirements(src, interpreter)
 
 
 @dataclass