diff --git a/pkgs/write-fennel/default.nix b/pkgs/write-fennel/default.nix
index df10f3b..67d1908 100644
--- a/pkgs/write-fennel/default.nix
+++ b/pkgs/write-fennel/default.nix
@@ -27,7 +27,7 @@ name :
        echo "#!${lua}/bin/lua ${luaFlags}"
        echo "package.path = ${lib.strings.escapeShellArg (builtins.concatStringsSep "" luapath)} .. package.path"
        echo "package.cpath = ${lib.strings.escapeShellArg (builtins.concatStringsSep "" luacpath)} .. package.cpath"
-       echo "require('posix.stdlib').setenv('PATH',${lib.escapeShellArg (lib.makeBinPath packages)} .. \":\" .. os.getenv('PATH'))"
+       echo "local ok, stdlib = pcall(require,'posix.stdlib'); if ok then stdlib.setenv('PATH',${lib.escapeShellArg (lib.makeBinPath packages)} .. \":\" .. os.getenv('PATH')) end"
        fennel ${if correlate then "--correlate" else ""} --compile ${source}
       ) >  ${name}.lua
     '';