diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -682,7 +682,8 @@
   endif()
 
   if (MSVC)
-    if (uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+    if ((NOT CMAKE_MSVC_RUNTIME_LIBRARY AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+        OR (CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "Debug"))
       set(LIB_SUFFIX "d")
     else()
       set(LIB_SUFFIX "")
diff --git a/libcxx/test/CMakeLists.txt b/libcxx/test/CMakeLists.txt
--- a/libcxx/test/CMakeLists.txt
+++ b/libcxx/test/CMakeLists.txt
@@ -59,7 +59,8 @@
     set(cxx_lib "libcpmt")
   endif()
 
-  if (uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+  if ((NOT CMAKE_MSVC_RUNTIME_LIBRARY AND uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+      OR (CMAKE_MSVC_RUNTIME_LIBRARY MATCHES "Debug"))
     set(dbg_include " -D_DEBUG -include set_windows_crt_report_mode.h")
     set(crt_lib "${crt_lib}d")
     set(cxx_lib "${cxx_lib}d")