diff --git a/src/demoreader.cpp b/src/demoreader.cpp
--- a/src/demoreader.cpp
+++ b/src/demoreader.cpp
@@ -19,6 +19,10 @@
 
 #include "demoreader.h"
 
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
 DemoReader::DemoReader(QIODevice* device, ChannelManager* channelMan, QObject *parent) :
     AbstractReader(device, channelMan, parent)
 {