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/configs/llvm-libc++-shared-clangcl.cfg.in b/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
@@ -13,7 +13,7 @@
     crt_lib = 'libcmt'
     cxx_lib = 'libcpmt'
 
-if '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG':
+if (runtime_library == '' and '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG') or 'Debug' in runtime_library:
     dbg_include = ' -D_DEBUG -include set_windows_crt_report_mode.h'
     crt_lib += 'd'
     cxx_lib += 'd'
diff --git a/libcxx/test/configs/llvm-libc++-shared-no-vcruntime-clangcl.cfg.in b/libcxx/test/configs/llvm-libc++-shared-no-vcruntime-clangcl.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared-no-vcruntime-clangcl.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared-no-vcruntime-clangcl.cfg.in
@@ -14,7 +14,7 @@
     crt_lib = 'libcmt'
     cxx_lib = 'libcpmt'
 
-if '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG':
+if (runtime_library == '' and '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG') or 'Debug' in runtime_library:
     dbg_include = ' -D_DEBUG -include set_windows_crt_report_mode.h'
     crt_lib += 'd'
     cxx_lib += 'd'
diff --git a/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in b/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
--- a/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
@@ -13,7 +13,7 @@
     crt_lib = 'libcmt'
     cxx_lib = 'libcpmt'
 
-if '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG':
+if (runtime_library == '' and '@uppercase_CMAKE_BUILD_TYPE@' == 'DEBUG') or 'Debug' in runtime_library:
     dbg_include = ' -D_DEBUG -include set_windows_crt_report_mode.h'
     crt_lib += 'd'
     cxx_lib += 'd'