diff --git a/include/tvm/ffi/object.h b/include/tvm/ffi/object.h
index 1f0fe4c1..28fd401d 100644
--- a/include/tvm/ffi/object.h
+++ b/include/tvm/ffi/object.h
@@ -26,6 +26,7 @@
 #include <tvm/ffi/base_details.h>
 #include <tvm/ffi/c_api.h>
 
+#include <cstddef>
 #include <optional>
 #include <string>
 #include <type_traits>
@@ -1094,8 +1095,8 @@ struct ObjectUnsafe {
 
   template <typename Class>
   TVM_FFI_INLINE static int64_t GetObjectOffsetToSubclass() {
-    return (reinterpret_cast<int64_t>(&(static_cast<Class*>(nullptr)->header_)) -
-            reinterpret_cast<int64_t>(&(static_cast<Object*>(nullptr)->header_)));
+    return static_cast<int64_t>(offsetof(Class, header_)) -
+           static_cast<int64_t>(offsetof(Object, header_));
   }
 
   template <typename T>
diff --git a/include/tvm/ffi/string.h b/include/tvm/ffi/string.h
index 9c1057a9..b2188452 100644
--- a/include/tvm/ffi/string.h
+++ b/include/tvm/ffi/string.h
@@ -754,7 +754,9 @@ class String {
   }
   void InitData(const char* data, size_t size) {
     char* dest_data = InitSpaceForSize(size);
-    std::memcpy(dest_data, data, size);
+    if (size > 0) {
+      std::memcpy(dest_data, data, size);
+    }
     dest_data[size] = '\0';
   }
   /*!