diff --git a/crates/erg_compiler/context/inquire.rs b/crates/erg_compiler/context/inquire.rs
index 24dc76eb..4409ad75 100644
--- a/crates/erg_compiler/context/inquire.rs
+++ b/crates/erg_compiler/context/inquire.rs
@@ -1361,8 +1361,9 @@ impl Context {
                 }
             }
         }
+        let mut checked = vec![];
         for ctx in self
-            .get_nominal_super_type_ctxs(obj.ref_t())
+            .get_nominal_super_type_ctxs(&obj.ref_t().lower_bounded())
             .ok_or_else(|| {
                 TyCheckError::type_not_found(
                     self.cfg.input.clone(),
@@ -1373,6 +1374,7 @@ impl Context {
                 )
             })?
         {
+            checked.push(&ctx.typ);
             if let Some(vi) = ctx.get_current_scope_non_param(&attr_name.name) {
                 self.validate_visibility(attr_name, vi, input, namespace)?;
                 return Ok(vi.clone());
@@ -1395,6 +1397,45 @@ impl Context {
                 }
             }
         }
+        if obj.ref_t() != &obj.ref_t().lower_bounded() {
+            for ctx in self
+                .get_nominal_super_type_ctxs(obj.ref_t())
+                .ok_or_else(|| {
+                    TyCheckError::type_not_found(
+                        self.cfg.input.clone(),
+                        line!() as usize,
+                        obj.loc(),
+                        self.caused_by(),
+                        obj.ref_t(),
+                    )
+                })?
+            {
+                if checked.contains(&&ctx.typ) {
+                    continue;
+                }
+                if let Some(vi) = ctx.get_current_scope_non_param(&attr_name.name) {
+                    self.validate_visibility(attr_name, vi, input, namespace)?;
+                    return Ok(vi.clone());
+                }
+                for methods_ctx in ctx.methods_list.iter() {
+                    if let Some(vi) = methods_ctx.get_current_scope_non_param(&attr_name.name) {
+                        self.validate_visibility(attr_name, vi, input, namespace)?;
+                        return Ok(vi.clone());
+                    }
+                }
+                if let Some(ctx) = self.get_same_name_context(&ctx.name) {
+                    match ctx.rec_get_var_info(attr_name, AccessKind::BoundAttr, input, namespace) {
+                        Triple::Ok(t) => {
+                            return Ok(t);
+                        }
+                        Triple::Err(e) => {
+                            return Err(e);
+                        }
+                        Triple::None => {}
+                    }
+                }
+            }
+        }
         match self.get_attr_type_by_name(obj, attr_name, namespace) {
             Triple::Ok(method) => {
                 let def_t = self
@@ -3013,6 +3054,7 @@ impl Context {
     /// ```erg
     /// get_nominal_super_type_ctx(Nat) == [<Nat>, <Int>, <Float>, ..., <Obj>, <Eq>, ...]
     /// get_nominal_super_type_ctx({Nat}) == [<Type>, <Obj>, <Eq>, ...]
+    /// get_nominal_super_type_ctx(?T(:> Nat, <: Eq)) == == [<Eq>, ...]
     /// ```
     pub fn get_nominal_super_type_ctxs<'a>(&'a self, t: &Type) -> Option<Vec<&'a TypeContext>> {
         match t {
diff --git a/tests/should_err/subtyping.er b/tests/should_err/subtyping.er
index a13f7091..39b62125 100644
--- a/tests/should_err/subtyping.er
+++ b/tests/should_err/subtyping.er
@@ -22,6 +22,12 @@ for! zip([1], ["a"]), ((i: Str, s: Str),) => # ERR
 for! zip([1], ["a"]), ((i, s),) =>
     k = i + "a" # ERR
     print! k
+for! zip([1], ["a"]), (is) =>
+    i = is[0]
+    s = is[1]
+    k = i + "a" # ERR
+    _ = s + 1 # ERR
+    print! k
 
 for! zip([1+1], ["a"+"b"]), ((i, s),) => # i: Nat, s: Str
     print! i + 1
diff --git a/tests/test.rs b/tests/test.rs
index a43b6422..596ca57a 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -716,7 +716,7 @@ fn exec_structural_err() -> Result<(), ()> {
 #[test]
 fn exec_subtyping_err() -> Result<(), ()> {
     // NOTE: The content of some errors is semantically redundant and can be reduced.
-    expect_failure("tests/should_err/subtyping.er", 3, 13)
+    expect_failure("tests/should_err/subtyping.er", 3, 15)
 }
 
 #[test]