diff --git a/src/backend/datasources/filters/AbstractFileFilter.h b/src/backend/datasources/filters/AbstractFileFilter.h
index e2604d7b4..2a45228c0 100644
--- a/src/backend/datasources/filters/AbstractFileFilter.h
+++ b/src/backend/datasources/filters/AbstractFileFilter.h
@@ -1,77 +1,77 @@
 /***************************************************************************
 File                 : AbstractFileFilter.h
 Project              : LabPlot
 Description          : file I/O-filter related interface
 --------------------------------------------------------------------
 Copyright            : (C) 2009-2018 Alexander Semke (alexander.semke@web.de)
 Copyright            : (C) 2017 Stefan Gerlach (stefan.gerlach@uni.kn)
 ***************************************************************************/
 
 /***************************************************************************
  *                                                                         *
  *  This program is free software; you can redistribute it and/or modify   *
  *  it under the terms of the GNU 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 General Public License for more details.                           *
  *                                                                         *
  *   You should have received a copy of the GNU General Public License     *
  *   along with this program; if not, write to the Free Software           *
  *   Foundation, Inc., 51 Franklin Street, Fifth Floor,                    *
  *   Boston, MA  02110-1301  USA                                           *
  *                                                                         *
  ***************************************************************************/
 
 #ifndef ABSTRACTFILEFILTER_H
 #define ABSTRACTFILEFILTER_H
 
 #include "backend/core/AbstractColumn.h"
 #include <QObject>
 #include <QLocale>
 #include <memory>	// smart pointer
 
 class AbstractDataSource;
 class XmlStreamReader;
 class QXmlStreamWriter;
 
 class AbstractFileFilter : public QObject {
 	Q_OBJECT
 	Q_ENUMS(FileType)
 	Q_ENUMS(ImportMode)
 
 public:
 	enum FileType {Ascii, Binary, Image, HDF5, NETCDF, FITS, JSON, ROOT, NgspiceRawAscii, NgspiceRawBinary};
 	enum ImportMode {Append, Prepend, Replace};
 
 	explicit AbstractFileFilter(FileType type) : m_type(type) {}
 	~AbstractFileFilter() override = default;
 
 	static bool isNan(QString);
 	static AbstractColumn::ColumnMode columnMode(const QString& valueString, const QString& dateTimeFormat, QLocale::Language);
 	static QStringList numberFormats();
 	static AbstractFileFilter::FileType fileType(const QString&);
 	static QStringList fileTypes();
 
 	virtual void readDataFromFile(const QString& fileName, AbstractDataSource* = nullptr, ImportMode = AbstractFileFilter::Replace) = 0;
 	virtual void write(const QString& fileName, AbstractDataSource*) = 0;
 
 	virtual void loadFilterSettings(const QString& filterName) = 0;
 	virtual void saveFilterSettings(const QString& filterName) const = 0;
 
 	virtual void save(QXmlStreamWriter*) const = 0;
 	virtual bool load(XmlStreamReader*) = 0;
 
-	constexpr FileType type() const { return m_type; }
+	FileType type() const { return m_type; }
 
 signals:
 	void completed(int) const; //!< int ranging from 0 to 100 notifies about the status of a read/write process
 
 protected:
 	const FileType m_type;
 };
 
 #endif