diff --git a/core/fpdfapi/parser/fpdf_parser_decode.cpp b/core/fpdfapi/parser/fpdf_parser_decode.cpp
index 7a9f798..e8bb21c 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode.cpp
@@ -256,7 +256,8 @@
         copy_len = buf_left;
         memset(*dest_buf + dest_count + copy_len, '\0', delta);
       }
-      memcpy(*dest_buf + dest_count, &src_span[i + 1], copy_len);
+      auto copy_span = src_span.subspan(i + 1, copy_len);
+      memcpy(*dest_buf + dest_count, copy_span.data(), copy_span.size());
       dest_count += src_span[i] + 1;
       i += src_span[i] + 2;
     } else {