diff --git a/modules/installer/tools/nixos-rebuild.sh b/modules/installer/tools/nixos-rebuild.sh
index d799ee6037d0..c5dce0a1807b 100644
--- a/modules/installer/tools/nixos-rebuild.sh
+++ b/modules/installer/tools/nixos-rebuild.sh
@@ -142,8 +142,8 @@ fi
 # more conservative.
 if test -n "$buildNix"; then
     echo "building Nix..." >&2
-    if ! nix-build $NIXOS -A nixFallback -o $tmpDir/nix > /dev/null; then
-        nix-build $NIXPKGS -A nixUnstable -o $tmpDir/nix > /dev/null
+    if ! nix-build $NIXOS -A nixFallback -o $tmpDir/nix $extraBuildFlags > /dev/null; then
+        nix-build $NIXPKGS -A nixUnstable -o $tmpDir/nix $extraBuildFlags > /dev/null
     fi
     PATH=$tmpDir/nix/bin:$PATH
 fi