diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a7d2e2bc..842103da1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -205,6 +205,7 @@ ELSEIF(MSVC)
   # for msvc, tell it to always use 8-byte pointers to member functions to avoid confusion
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /vmg /vmm /MP")
   SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} /Od")
+  STRING(REPLACE "/O2" "" CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
   STRING(REPLACE "/DNDEBUG" "" CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
 ENDIF()