diff --git a/rust/nix-expr/src/eval_state.rs b/rust/nix-expr/src/eval_state.rs
index d99f50d..7ba139a 100644
--- a/rust/nix-expr/src/eval_state.rs
+++ b/rust/nix-expr/src/eval_state.rs
@@ -225,12 +225,12 @@ impl EvalState {
         let attr_name = CString::new(attr_name)
             .with_context(|| "require_attrs_select_opt: attrName contains null byte")?;
         let v2 = unsafe {
-            check_call_opt_key!(raw::get_attr_byname[
+            check_call_opt_key!(raw::get_attr_byname(
                 &mut self.context,
                 v.raw_ptr(),
                 self.eval_state.as_ptr(),
                 attr_name.as_ptr()
-            ])
+            ))
         }?;
         Ok(v2.map(Value::new))
     }
diff --git a/rust/nix-util/src/context.rs b/rust/nix-util/src/context.rs
index 1314360..f5db84d 100644
--- a/rust/nix-util/src/context.rs
+++ b/rust/nix-util/src/context.rs
@@ -105,10 +105,10 @@ pub use check_call;
 // TODO: Generalize this macro to work with any error code or any error handling logic
 #[macro_export]
 macro_rules! check_call_opt_key {
-    ($f:path[$ctx:expr, $($arg:expr),*]) => {
+    ($($f:ident)::+($ctx:expr, $($arg:expr),*)) => {
         {
             let ctx : &mut $crate::context::Context = $ctx;
-            let ret = $f(ctx.ptr(), $($arg,)*);
+            let ret = $($f)::*(ctx.ptr(), $($arg,)*);
             if unsafe { raw::err_code(ctx.ptr()) == raw::NIX_ERR_KEY } {
                 ctx.clear();
                 return Ok(None);