diff --git a/cpp/std/string.go b/cpp/std/string.go
index 5427a51a..5f3b2105 100644
--- a/cpp/std/string.go
+++ b/cpp/std/string.go
@@ -31,7 +31,7 @@ type StringView = string
 
 // String represents a C++ std::string object.
 type String struct {
-	Unused [3]uintptr
+	Unused [3 * unsafe.Sizeof(0)]byte
 }
 
 // llgo:link (*String).InitEmpty C.stdStringInitEmpty