diff --git a/Device/Instrument/Instrument.h b/Device/Instrument/Instrument.h
index 51c9038f5ddbb4b6a82dd0baab4290457a0a6087..c5dd09a1196200730dd0e34c7b12250496a1ada1 100644
--- a/Device/Instrument/Instrument.h
+++ b/Device/Instrument/Instrument.h
@@ -26,7 +26,6 @@
 class Beam;
 class CoordSystem2D;
 class IDetector;
-class IDetector2D;
 
 //! Assembles beam, detector and their relative positions with respect to the sample.