diff --git a/simgear/math/SGQuat.hxx b/simgear/math/SGQuat.hxx
index 93f071ef..b65de8dc 100644
--- a/simgear/math/SGQuat.hxx
+++ b/simgear/math/SGQuat.hxx
@@ -26,11 +26,6 @@
 #undef max
 #endif
 
-// for microsoft compiler
-#ifdef _MSC_VER
-#define copysign _copysign
-#endif
-
 #include <osg/Quat>
 
 template<typename T>