diff --git a/third_party/nix/CMakeLists.txt b/third_party/nix/CMakeLists.txt
index e37bef938..200b604c2 100644
--- a/third_party/nix/CMakeLists.txt
+++ b/third_party/nix/CMakeLists.txt
@@ -40,7 +40,9 @@ if (CLANG_TIDY_PATH)
   endif()
 endif()
 
-if (NOT SANDBOX_SHELL)
+if (DEFINED ENV{SANDBOX_SHELL})
+  set(SANDBOX_SHELL ENV{SANDBOX_SHELL})
+else()
   find_program(BUSYBOX busybox)
   if (BUSYBOX)
     set(SANDBOX_SHELL "${BUSYBOX}")
diff --git a/third_party/nix/default.nix b/third_party/nix/default.nix
index 1056a3cbb..f9ed4749e 100644
--- a/third_party/nix/default.nix
+++ b/third_party/nix/default.nix
@@ -95,8 +95,7 @@ in lib.fix (self: pkgs.llvmPackages.libcxxStdenv.mkDerivation {
       -DCMAKE_BUILD_TYPE=RelWithDebInfo \
       -DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF \
       -DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF \
-      -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON \
-      -DSANDBOX_SHELL=${pkgs.busybox}/bin/busybox
+      -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON
   '';
 
   installCheckPhase = ''