diff --git a/src/engine.rs b/src/engine.rs
index 3b740b71..0fdd0467 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -1064,7 +1064,7 @@ impl Engine {
                 // xxx.prop[expr] | xxx.prop.expr
                 Expr::Index(x) | Expr::Dot(x) => {
                     let (prop, expr, pos) = x.as_ref();
-                    let is_idx = matches!(expr, Expr::Index(_));
+                    let is_idx = matches!(rhs, Expr::Index(_));
                     let args = &mut [obj, &mut Default::default()];
 
                     let (mut val, updated) = if let Expr::Property(p) = prop {
@@ -1102,7 +1102,7 @@ impl Engine {
                 }
                 // Syntax error
                 _ => Err(Box::new(EvalAltResult::ErrorDotExpr(
-                    "".into(),
+                    format!("{:?}", rhs),
                     rhs.position(),
                 ))),
             }
diff --git a/tests/maps.rs b/tests/maps.rs
index 64c5a4c2..a7aef8dd 100644
--- a/tests/maps.rs
+++ b/tests/maps.rs
@@ -21,6 +21,10 @@ fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
             )?,
             'o'
         );
+        assert_eq!(
+            engine.eval::<String>(r#"let a = [#{s:"hello"}]; a[0].s[2] = 'X'; a[0].s"#)?,
+            "heXlo"
+        );
     }
 
     assert_eq!(