diff --git a/README.md b/README.md
index 14d934f8..d2eb0f10 100644
--- a/README.md
+++ b/README.md
@@ -163,6 +163,13 @@ nix-shell> nixpkgs-review comments
 `nixpkgs-review` will by default use [nix-output-monitor](https://github.com/maralorn/nix-output-monitor) if found in `$PATH`.
 If you have `nom` installed but don't want to use it, you can pass `nix` to `--build-graph` to use `nix build` instead of `nom build`.
 
+Some pull requests may require configuration for nixpkgs to test out. You can
+use the `--extra-nixpkgs-config` flag to supply extra configuration for nixpkgs.
+
+```console
+$ nixpkgs-review pr 37242 --extra-nixpkgs-config '{ cudaSupport = true; }'
+```
+
 ## Using nixpkgs-review in scripts or other programs
 
 After building, `nixpkgs-review` will normally start a `nix-shell` with the
diff --git a/nixpkgs_review/buildenv.py b/nixpkgs_review/buildenv.py
index f73a2584..17e264cc 100644
--- a/nixpkgs_review/buildenv.py
+++ b/nixpkgs_review/buildenv.py
@@ -1,6 +1,6 @@
-from dataclasses import dataclass
 import os
 import sys
+from pathlib import Path
 from tempfile import NamedTemporaryFile
 from typing import Any, Optional
 
@@ -20,11 +20,32 @@ def find_nixpkgs_root() -> Optional[str]:
         prefix.append("..")
 
 
-@dataclass
 class Buildenv:
-    allow_aliases: bool
+    def __init__(self, allow_aliases: bool, extra_nixpkgs_config: str) -> None:
+        if not (
+            extra_nixpkgs_config.startswith("{") and extra_nixpkgs_config.endswith("}")
+        ):
+            raise RuntimeError(
+                "--extra-nixpkgs-config must start with `{` and end with `}`"
+            )
+
+        self.nixpkgs_config = NamedTemporaryFile(suffix=".nix")
+        self.nixpkgs_config.write(
+            str.encode(
+                f"""{{
+  allowUnfree = true;
+  allowBroken = true;
+  {"allowAliases = false;" if not allow_aliases else ""}
+  checkMeta = true;
+  ## TODO: also build packages marked as insecure
+  # allowInsecurePredicate = x: true;
+}} // {extra_nixpkgs_config}
+"""
+            )
+        )
+        self.nixpkgs_config.flush()
 
-    def __enter__(self) -> None:
+    def __enter__(self) -> Path:
         self.environ = os.environ.copy()
         self.old_cwd = os.getcwd()
 
@@ -35,20 +56,8 @@ def __enter__(self) -> None:
         else:
             os.chdir(root)
 
-        self.nixpkgs_config = NamedTemporaryFile()
-        self.nixpkgs_config.write(
-            str.encode(
-                f"""{{
-          allowUnfree = true;
-          allowBroken = true;
-          {"allowAliases = false;" if not self.allow_aliases else ""}
-          ## TODO also build packages marked as insecure
-          #allowInsecurePredicate = x: true;
-        }}"""
-            )
-        )
-        self.nixpkgs_config.flush()
         os.environ["NIXPKGS_CONFIG"] = self.nixpkgs_config.name
+        return Path(self.nixpkgs_config.name)
 
     def __exit__(self, _type: Any, _value: Any, _traceback: Any) -> None:
         if self.old_cwd is not None:
diff --git a/nixpkgs_review/cli/__init__.py b/nixpkgs_review/cli/__init__.py
index c2fd1b9c..474b67fc 100644
--- a/nixpkgs_review/cli/__init__.py
+++ b/nixpkgs_review/cli/__init__.py
@@ -5,6 +5,7 @@
 from pathlib import Path
 from typing import Any, List, Optional, Pattern, cast
 
+from ..utils import current_system, nix_nom_tool
 from .approve import approve_command
 from .comments import show_comments
 from .merge import merge_command
@@ -12,7 +13,6 @@
 from .pr import pr_command
 from .rev import rev_command
 from .wip import wip_command
-from ..utils import current_system, nix_nom_tool
 
 
 def regex_type(s: str) -> Pattern[str]:
@@ -235,6 +235,12 @@ def common_flags() -> List[CommonFlag]:
             action="store_true",
             help="Print the nixpkgs-review results to stdout",
         ),
+        CommonFlag(
+            "--extra-nixpkgs-config",
+            type=str,
+            default="{ }",
+            help="Extra nixpkgs config to pass to `import <nixpkgs>`",
+        ),
     ]
 
 
diff --git a/nixpkgs_review/cli/pr.py b/nixpkgs_review/cli/pr.py
index 5e30cbe8..75e4d1bc 100644
--- a/nixpkgs_review/cli/pr.py
+++ b/nixpkgs_review/cli/pr.py
@@ -46,7 +46,9 @@ def pr_command(args: argparse.Namespace) -> str:
 
     allow = AllowedFeatures(args.allow)
 
-    with Buildenv(allow.aliases), ExitStack() as stack:
+    with Buildenv(
+        allow.aliases, args.extra_nixpkgs_config
+    ) as nixpkgs_config, ExitStack() as stack:
         for pr in prs:
             builddir = stack.enter_context(Builddir(f"pr-{pr}"))
             try:
@@ -67,6 +69,8 @@ def pr_command(args: argparse.Namespace) -> str:
                     checkout=checkout_option,
                     sandbox=args.sandbox,
                     build_graph=args.build_graph,
+                    nixpkgs_config=nixpkgs_config,
+                    extra_nixpkgs_config=args.extra_nixpkgs_config,
                 )
                 contexts.append((pr, builddir.path, review.build_pr(pr)))
             except subprocess.CalledProcessError:
diff --git a/nixpkgs_review/cli/rev.py b/nixpkgs_review/cli/rev.py
index 6d6f94f1..37018399 100644
--- a/nixpkgs_review/cli/rev.py
+++ b/nixpkgs_review/cli/rev.py
@@ -9,8 +9,13 @@
 
 def rev_command(args: argparse.Namespace) -> Path:
     allow = AllowedFeatures(args.allow)
-    with Buildenv(allow.aliases):
+    with Buildenv(allow.aliases, args.extra_nixpkgs_config) as nixpkgs_config:
         commit = verify_commit_hash(args.commit)
         return review_local_revision(
-            f"rev-{commit}", args, allow, commit, print_result=args.print_result
+            f"rev-{commit}",
+            args,
+            allow,
+            nixpkgs_config,
+            commit,
+            print_result=args.print_result,
         )
diff --git a/nixpkgs_review/cli/wip.py b/nixpkgs_review/cli/wip.py
index 77c3484b..6377d7e5 100644
--- a/nixpkgs_review/cli/wip.py
+++ b/nixpkgs_review/cli/wip.py
@@ -9,11 +9,12 @@
 
 def wip_command(args: argparse.Namespace) -> Path:
     allow = AllowedFeatures(args.allow)
-    with Buildenv(allow.aliases):
+    with Buildenv(allow.aliases, args.extra_nixpkgs_config) as nixpkgs_config:
         return review_local_revision(
             "rev-%s-dirty" % verify_commit_hash("HEAD"),
             args,
             allow,
+            nixpkgs_config,
             None,
             args.staged,
             args.print_result,
diff --git a/nixpkgs_review/nix.py b/nixpkgs_review/nix.py
index 495df4d2..25a6adb6 100644
--- a/nixpkgs_review/nix.py
+++ b/nixpkgs_review/nix.py
@@ -46,6 +46,7 @@ def nix_shell(
     cache_directory: Path,
     system: str,
     build_graph: str,
+    nixpkgs_config: Path,
     run: Optional[str] = None,
     sandbox: bool = False,
 ) -> None:
@@ -54,7 +55,7 @@ def nix_shell(
         raise RuntimeError(f"{build_graph} not found in PATH")
 
     shell = cache_directory.joinpath("shell.nix")
-    write_shell_expression(shell, attrs, system)
+    write_shell_expression(shell, attrs, system, nixpkgs_config)
     if sandbox:
         args = _nix_shell_sandbox(nix_shell, shell)
     else:
@@ -189,7 +190,6 @@ def nix_eval(
         json.dump(list(attrs), attr_json)
         eval_script = str(ROOT.joinpath("nix/evalAttrs.nix"))
         attr_json.flush()
-        allowAliases = "true" if allow.aliases else "false"
         cmd = [
             "nix",
             "--extra-experimental-features",
@@ -203,7 +203,7 @@ def nix_eval(
             if allow.ifd
             else "--no-allow-import-from-derivation",
             "--expr",
-            f"(import {eval_script} {{ allowAliases = {allowAliases}; attr-json = {attr_json.name}; }})",
+            f"(import {eval_script} {{ attr-json = {attr_json.name}; }})",
         ]
 
         try:
@@ -231,6 +231,7 @@ def nix_build(
     system: str,
     allow: AllowedFeatures,
     build_graph: str,
+    nixpkgs_config: Path,
 ) -> List[Attr]:
     if not attr_names:
         info("Nothing to be built.")
@@ -246,7 +247,7 @@ def nix_build(
         return attrs
 
     build = cache_directory.joinpath("build.nix")
-    write_shell_expression(build, filtered, system)
+    write_shell_expression(build, filtered, system, nixpkgs_config)
 
     command = [
         build_graph,
@@ -280,10 +281,12 @@ def nix_build(
     return attrs
 
 
-def write_shell_expression(filename: Path, attrs: List[str], system: str) -> None:
+def write_shell_expression(
+    filename: Path, attrs: List[str], system: str, nixpkgs_config: Path
+) -> None:
     with open(filename, "w+") as f:
         f.write(
-            f"""{{ pkgs ? import ./nixpkgs {{ system = \"{system}\"; }} }}:
+            f"""{{ pkgs ? import ./nixpkgs {{ system = \"{system}\"; config = import {nixpkgs_config}; }} }}:
 with pkgs;
 let
   paths = [
diff --git a/nixpkgs_review/nix/evalAttrs.nix b/nixpkgs_review/nix/evalAttrs.nix
index cb2f7806..a46dd9a3 100644
--- a/nixpkgs_review/nix/evalAttrs.nix
+++ b/nixpkgs_review/nix/evalAttrs.nix
@@ -1,8 +1,9 @@
-{ allowAliases ? false, attr-json }:
+{ attr-json }:
 
 with builtins;
 let
-  pkgs = import <nixpkgs> { config = { checkMeta = true; allowUnfree = true; inherit allowAliases; }; };
+  pkgs = import <nixpkgs> { };
+
   inherit (pkgs) lib;
 
   attrs = fromJSON (readFile attr-json);
diff --git a/nixpkgs_review/report.py b/nixpkgs_review/report.py
index dd5018c1..157af0e3 100644
--- a/nixpkgs_review/report.py
+++ b/nixpkgs_review/report.py
@@ -1,6 +1,6 @@
+import json
 import os
 import subprocess
-import json
 from pathlib import Path
 from typing import Callable, List, Optional
 
@@ -86,7 +86,9 @@ def write_error_logs(attrs: List[Attr], directory: Path) -> None:
 
 
 class Report:
-    def __init__(self, system: str, attrs: List[Attr]) -> None:
+    def __init__(
+        self, system: str, attrs: List[Attr], extra_nixpkgs_config: str
+    ) -> None:
         self.system = system
         self.attrs = attrs
         self.broken: List[Attr] = []
@@ -96,6 +98,11 @@ def __init__(self, system: str, attrs: List[Attr]) -> None:
         self.tests: List[Attr] = []
         self.built: List[Attr] = []
 
+        if extra_nixpkgs_config != "{ }":
+            self.extra_nixpkgs_config: Optional[str] = extra_nixpkgs_config
+        else:
+            self.extra_nixpkgs_config = None
+
         for a in attrs:
             if a.broken:
                 self.broken.append(a)
@@ -134,6 +141,7 @@ def serialize_attrs(attrs: List[Attr]) -> List[str]:
             {
                 "system": self.system,
                 "pr": pr,
+                "extra-nixpkgs-config": self.extra_nixpkgs_config,
                 "broken": serialize_attrs(self.broken),
                 "non-existant": serialize_attrs(self.non_existant),
                 "blacklisted": serialize_attrs(self.blacklisted),
@@ -149,6 +157,8 @@ def markdown(self, pr: Optional[int]) -> str:
         cmd = "nixpkgs-review"
         if pr is not None:
             cmd += f" pr {pr}"
+        if self.extra_nixpkgs_config:
+            cmd += f" --extra-nixpkgs-config '{self.extra_nixpkgs_config}'"
 
         msg = f"Result of `{cmd}` run on {self.system} [1](https://github.com/Mic92/nixpkgs-review)\n"
 
diff --git a/nixpkgs_review/review.py b/nixpkgs_review/review.py
index 2db8948f..d81a9568 100644
--- a/nixpkgs_review/review.py
+++ b/nixpkgs_review/review.py
@@ -88,6 +88,8 @@ def __init__(
         system: str,
         allow: AllowedFeatures,
         build_graph: str,
+        nixpkgs_config: Path,
+        extra_nixpkgs_config: str,
         api_token: Optional[str] = None,
         use_ofborg_eval: Optional[bool] = True,
         only_packages: Set[str] = set(),
@@ -113,6 +115,8 @@ def __init__(
         self.allow = allow
         self.sandbox = sandbox
         self.build_graph = build_graph
+        self.nixpkgs_config = nixpkgs_config
+        self.extra_nixpkgs_config = extra_nixpkgs_config
 
     def worktree_dir(self) -> str:
         return str(self.builddir.worktree_dir)
@@ -145,6 +149,7 @@ def build_commit(
         Review a local git commit
         """
         self.git_worktree(base_commit)
+
         base_packages = list_packages(
             str(self.worktree_dir()),
             self.system,
@@ -195,6 +200,7 @@ def build(self, packages: Set[str], args: str) -> List[Attr]:
             self.system,
             self.allow,
             self.build_graph,
+            self.nixpkgs_config,
         )
 
     def build_pr(self, pr_number: int) -> List[Attr]:
@@ -241,7 +247,7 @@ def start_review(
         os.environ["NIX_PATH"] = path.as_posix()
         if pr:
             os.environ["PR"] = str(pr)
-        report = Report(self.system, attr)
+        report = Report(self.system, attr, self.extra_nixpkgs_config)
         report.print_console(pr)
         report.write(path, pr)
 
@@ -259,6 +265,7 @@ def start_review(
                 path,
                 self.system,
                 self.build_graph,
+                self.nixpkgs_config,
                 self.run,
                 self.sandbox,
             )
@@ -500,6 +507,7 @@ def review_local_revision(
     builddir_path: str,
     args: argparse.Namespace,
     allow: AllowedFeatures,
+    nixpkgs_config: Path,
     commit: Optional[str],
     staged: bool = False,
     print_result: bool = False,
@@ -516,6 +524,8 @@ def review_local_revision(
             system=args.system,
             allow=allow,
             build_graph=args.build_graph,
+            nixpkgs_config=nixpkgs_config,
+            extra_nixpkgs_config=args.extra_nixpkgs_config,
         )
         review.review_commit(builddir.path, args.branch, commit, staged, print_result)
         return builddir.path