diff --git a/stdlib/public/SwiftShims/DispatchOverlayShims.h b/stdlib/public/SwiftShims/DispatchOverlayShims.h
index e9eeebfeb75f6..d49e9ad38263c 100644
--- a/stdlib/public/SwiftShims/DispatchOverlayShims.h
+++ b/stdlib/public/SwiftShims/DispatchOverlayShims.h
@@ -215,8 +215,8 @@ static inline unsigned int
 _swift_dispatch_data_apply(
     __swift_shims_dispatch_data_t data,
     __swift_shims_dispatch_data_applier SWIFT_DISPATCH_NOESCAPE applier) {
-  return dispatch_data_apply(data, ^bool(dispatch_data_t data, size_t off, const void *loc, size_t size){
-    return applier(data, off, loc, size);
+  return dispatch_data_apply((dispatch_data_t)data, ^bool(dispatch_data_t data, size_t off, const void *loc, size_t size){
+    return applier((__swift_shims_dispatch_data_t)data, off, loc, size);
   });
 }