diff --git a/CMakeLists.txt b/CMakeLists.txt
index a608e42dab..ce29a65dde 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -151,6 +151,7 @@ endif()
 # We _want_ assertions in RelWithDebInfo build-type.
 if(CMAKE_C_FLAGS_RELWITHDEBINFO MATCHES DNDEBUG)
   string(REPLACE "-DNDEBUG" "" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO}")
+  string(REPLACE "/DNDEBUG" "" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO}")
 endif()
 
 option(LOG_LIST_ACTIONS "Add list actions logging" OFF)