diff --git a/cmake/setup.cmake b/cmake/setup.cmake
index 26079f31..0ad84df9 100644
--- a/cmake/setup.cmake
+++ b/cmake/setup.cmake
@@ -4,6 +4,8 @@
 # give a #error if this manoeuvre doesn't do what it needs to.
 string(REPLACE "/DNDEBUG" "" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
 string(REPLACE "-DNDEBUG" "" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
+string(REPLACE "/DNDEBUG" "" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE}")
+string(REPLACE "-DNDEBUG" "" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELEASE}")
 
 set(PUTTY_IPV6 ON
   CACHE BOOL "Build PuTTY with IPv6 support if possible")