diff --git a/pkgs/build-support/build-bazel-package/default.nix b/pkgs/build-support/build-bazel-package/default.nix
index 07d37451ddf..26f44b922cd 100644
--- a/pkgs/build-support/build-bazel-package/default.nix
+++ b/pkgs/build-support/build-bazel-package/default.nix
@@ -25,7 +25,13 @@ in stdenv.mkDerivation (fBuildAttrs // {
     buildPhase = fFetchAttrs.buildPhase or ''
       runHook preBuild
 
-      bazel --output_base="$bazelOut" --output_user_root="$bazelUserRoot" fetch $bazelFlags $bazelTarget
+      # Bazel computes the default value of output_user_root before parsing the
+      # flag. The computation of the default value involves getting the $USER
+      # from the environment. I don't have that variable when building with
+      # sandbox enabled. Code here
+      # https://github.com/bazelbuild/bazel/blob/9323c57607d37f9c949b60e293b573584906da46/src/main/cpp/startup_options.cc#L123-L124
+      #
+      USER=homeless-shelter bazel --output_base="$bazelOut" --output_user_root="$bazelUserRoot" fetch $bazelFlags $bazelTarget
 
       runHook postBuild
     '';