diff --git a/sql/field.h b/sql/field.h
index 26092c12372..7f71fd2aec8 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -763,6 +763,7 @@ public:
   uint32 pack_length() const { return sizeof(double); }
   void sql_type(String &str) const;
   uint32 max_length() { return 53; }
+  uint size_of() const { return sizeof(*this); }
 };