diff --git a/cmake/modules/SwiftSharedCMakeConfig.cmake b/cmake/modules/SwiftSharedCMakeConfig.cmake
index a832224ece6e8..5c2db0f3cf9cd 100644
--- a/cmake/modules/SwiftSharedCMakeConfig.cmake
+++ b/cmake/modules/SwiftSharedCMakeConfig.cmake
@@ -81,7 +81,9 @@ macro(swift_common_standalone_build_config_llvm product is_cross_compiling)
   # HACK: this ugly tweaking is to prevent the propagation of the flag from LLVM
   # into swift.  The use of this flag pollutes all targets, and we are not able
   # to remove it on a per-target basis which breaks cross-compilation.
-  string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+  if("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
+    string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+  endif()
 
   set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
   string(REGEX REPLACE "([0-9]+)\\.[0-9]+(\\.[0-9]+)?" "\\1" PACKAGE_VERSION_MAJOR
diff --git a/stdlib/public/SwiftRemoteMirror/CMakeLists.txt b/stdlib/public/SwiftRemoteMirror/CMakeLists.txt
index 260d04e0f9d4a..6aa7709547909 100644
--- a/stdlib/public/SwiftRemoteMirror/CMakeLists.txt
+++ b/stdlib/public/SwiftRemoteMirror/CMakeLists.txt
@@ -1,3 +1,6 @@
+# HACK: Force this library to build with undefined symbols.
+string(REGEX REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+
 # libswiftRemoteMirror.dylib should not have runtime dependencies; it's
 # always built as a shared library.
 if(SWIFT_BUILD_DYNAMIC_STDLIB OR SWIFT_BUILD_REMOTE_MIRROR)