diff --git a/src/osm/o5mparser.h b/src/osm/o5mparser.h
index 957fbd9..8b4b048 100644
--- a/src/osm/o5mparser.h
+++ b/src/osm/o5mparser.h
@@ -1,63 +1,64 @@
 /*
     Copyright (C) 2020 Volker Krause <vkrause@kde.org>
 
     This program is free software; you can redistribute it and/or modify it
     under the terms of the GNU Library General Public License as published by
     the Free Software Foundation; either version 2 of the License, or (at your
     option) any later version.
 
     This program is distributed in the hope that it will be useful, but WITHOUT
     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
     License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
 #ifndef OSM_O5MPARSER_H
 #define OSM_O5MPARSER_H
 
+#include <cstddef>
 #include <cstdint>
 
 class O5mParserTest;
 
 namespace OSM {
 
 class DataSet;
 
 /** Zero-copy parser of O5M binary files.
  *  @see https://wiki.openstreetmap.org/wiki/O5m
  */
 class O5mParser
 {
 public:
     explicit O5mParser(DataSet *dataSet);
 
     /** Parse the given binary content.
      *  Feed this with QFile::map() for example.
      */
     void parse(const uint8_t *data, std::size_t len);
 
 private:
     friend class ::O5mParserTest;
 
     uint64_t readUnsigned(const uint8_t *&it, const uint8_t *endIt) const;
     int64_t readSigned(const uint8_t *&it, const uint8_t *endIt) const;
     template <typename T>
     T readDelta(const uint8_t *&it, const uint8_t *endIt, T &deltaState);
 
     void parseNode(const uint8_t *begin, const uint8_t *end);
 
     DataSet *m_dataSet = nullptr;
 
     // delta coding state
     void resetDeltaCodingState();
     int64_t m_nodeIdDelta = 0;
     int32_t m_latDelata = 0; // this can overflow, but that is intentional according to the spec!
     int32_t m_lonDelta = 0;
 };
 
 }
 
 #endif // OSM_O5MPARSER_H