diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index b81c98868..b4206033c 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -394,7 +394,7 @@ int main(int argc, char ** argv)
                 auto tmp = getEnv("TMPDIR", getEnv("XDG_RUNTIME_DIR", "/tmp"));
 
                 if (pure) {
-                    std::set<string> keepVars{"HOME", "USER", "LOGNAME", "DISPLAY", "PATH", "TERM", "IN_NIX_SHELL", "TZ", "PAGER", "NIX_BUILD_SHELL"};
+                    std::set<string> keepVars{"HOME", "USER", "LOGNAME", "DISPLAY", "PATH", "TERM", "IN_NIX_SHELL", "TZ", "PAGER", "NIX_BUILD_SHELL", "SHLVL"};
                     decltype(env) newEnv;
                     for (auto & i : env)
                         if (keepVars.count(i.first))