diff --git a/ecmascript/transforms/src/typescript/mod.rs b/ecmascript/transforms/src/typescript/mod.rs
index 66c9997cb30..f723d801666 100644
--- a/ecmascript/transforms/src/typescript/mod.rs
+++ b/ecmascript/transforms/src/typescript/mod.rs
@@ -229,6 +229,22 @@ impl Fold<Vec<ModuleItem>> for Strip {
                 decl: Decl::TsTypeAlias(..),
                 ..
             }))
+            | ModuleItem::ModuleDecl(ModuleDecl::ExportDecl(ExportDecl {
+                decl:
+                    Decl::Fn(FnDecl {
+                        function: Function { body: None, .. },
+                        ..
+                    }),
+                ..
+            }))
+            | ModuleItem::ModuleDecl(ModuleDecl::ExportDefaultDecl(ExportDefaultDecl {
+                decl:
+                    DefaultDecl::Fn(FnExpr {
+                        function: Function { body: None, .. },
+                        ..
+                    }),
+                ..
+            }))
             | ModuleItem::ModuleDecl(ModuleDecl::ExportDefaultDecl(ExportDefaultDecl {
                 decl: DefaultDecl::TsInterfaceDecl(..),
                 ..
@@ -349,7 +365,11 @@ impl Fold<Ident> for Strip {
             .imported_idents
             .entry((i.sym.clone(), i.span.ctxt()))
             .and_modify(|v| v.has_concrete = true);
-        i.fold_children(self)
+
+        Ident {
+            optional: false,
+            ..i.fold_children(self)
+        }
     }
 }
 
diff --git a/ecmascript/transforms/src/typescript/tests.rs b/ecmascript/transforms/src/typescript/tests.rs
index 9c6f6322e9e..57b63f2a83b 100644
--- a/ecmascript/transforms/src/typescript/tests.rs
+++ b/ecmascript/transforms/src/typescript/tests.rs
@@ -89,6 +89,47 @@ to!(
     "function foo($scope){}"
 );
 
+to!(
+    issue_357,
+    "export function addProp<T, K extends string, V>(
+  obj: T,
+  prop: K,
+  value: V
+): T & { [x in K]: V };
+export function addProp<T, K extends string, V>(
+  prop: K,
+  value: V
+): (obj: T) => T & { [x in K]: V };
+
+export function addProp(arg1: any, arg2: any, arg3?: any): any {
+  if (arguments.length === 2) {
+    return (object: any) => _addProp(object, arg1, arg2);
+  }
+  return _addProp(arg1, arg2, arg3);
+}
+
+function _addProp(obj: any, prop: string, value: any) {
+  return {
+    ...obj,
+    [prop]: value,
+  };
+}",
+    "export function addProp(arg1, arg2, arg3) {
+  if (arguments.length === 2) {
+    return (object) => _addProp(object, arg1, arg2);
+  }
+  return _addProp(arg1, arg2, arg3);
+}
+
+function _addProp(obj, prop, value) {
+  return {
+    ...obj,
+    [prop]: value,
+  };
+}
+"
+);
+
 to!(
     issue_366_01,
     "