diff --git a/apps/opencs/CMakeLists.txt b/apps/opencs/CMakeLists.txt
index c5f18656c..6e5b7b7c9 100644
--- a/apps/opencs/CMakeLists.txt
+++ b/apps/opencs/CMakeLists.txt
@@ -230,7 +230,6 @@ if (MSVC)
     if (CMAKE_CL_64)
         set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /bigobj")
     endif (CMAKE_CL_64)
-    add_definitions("-D_USE_MATH_DEFINES")
 	target_link_libraries(openmw-cs imm32.lib winmm.lib version.lib)
 endif (MSVC)