diff --git a/crates/oxc_isolated_declarations/src/scope.rs b/crates/oxc_isolated_declarations/src/scope.rs
index 94a347ca5..0b95dd379 100644
--- a/crates/oxc_isolated_declarations/src/scope.rs
+++ b/crates/oxc_isolated_declarations/src/scope.rs
@@ -261,10 +261,9 @@ impl<'a> Visit<'a> for ScopeTree<'a> {
         }
     }
 
-    /// `type D<T> = { [K in keyof T]: K };`
+    /// `type D = { [key in keyof T]: K };`
     ///             ^^^^^^^^^^^^^^^^^^^^
-    ///                `K` is a type parameter
-    /// We need to add `K` to the scope
+    /// We need to add both `T` and `K` to the scope
     fn visit_ts_mapped_type(&mut self, ty: &TSMappedType<'a>) {
         // copy from walk_ts_mapped_type
         self.enter_scope(ScopeFlags::empty());
@@ -272,6 +271,9 @@ impl<'a> Visit<'a> for ScopeTree<'a> {
         if let Some(name) = &ty.name_type {
             self.visit_ts_type(name);
         }
+        if let Some(constraint) = &ty.type_parameter.constraint {
+            self.visit_ts_type(constraint);
+        }
         if let Some(type_annotation) = &ty.type_annotation {
             self.visit_ts_type(type_annotation);
         }
diff --git a/crates/oxc_isolated_declarations/tests/fixtures/mapped-types.ts b/crates/oxc_isolated_declarations/tests/fixtures/mapped-types.ts
new file mode 100644
index 000000000..adcdd2418
--- /dev/null
+++ b/crates/oxc_isolated_declarations/tests/fixtures/mapped-types.ts
@@ -0,0 +1,6 @@
+import {K} from 'foo'
+import {T} from 'bar'
+
+export interface I {
+	prop: {[key in K]: T}
+}
\ No newline at end of file
diff --git a/crates/oxc_isolated_declarations/tests/snapshots/mapped-types.snap b/crates/oxc_isolated_declarations/tests/snapshots/mapped-types.snap
new file mode 100644
index 000000000..1f783ec23
--- /dev/null
+++ b/crates/oxc_isolated_declarations/tests/snapshots/mapped-types.snap
@@ -0,0 +1,11 @@
+---
+source: crates/oxc_isolated_declarations/tests/mod.rs
+input_file: crates/oxc_isolated_declarations/tests/fixtures/mapped-types.ts
+---
+==================== .D.TS ====================
+
+import { K } from 'foo';
+import { T } from 'bar';
+export interface I {
+	prop: { [key in K] : T};
+}