diff --git a/ext/sqlite3/database.c b/ext/sqlite3/database.c
index 0358e8a3..21be26c7 100644
--- a/ext/sqlite3/database.c
+++ b/ext/sqlite3/database.c
@@ -31,7 +31,7 @@ static char *
 utf16_string_value_ptr(VALUE str)
 {
   StringValue(str);
-  rb_str_buf_cat(str, "\x00", 1L);
+  rb_str_buf_cat(str, "\x00\x00", 2L);
   return RSTRING_PTR(str);
 }