diff --git a/lib/Basic/LangOptions.cpp b/lib/Basic/LangOptions.cpp
index 048f014fb7a35..4b0c4c1ba7b6d 100644
--- a/lib/Basic/LangOptions.cpp
+++ b/lib/Basic/LangOptions.cpp
@@ -327,6 +327,12 @@ std::pair<bool, bool> LangOptions::setTarget(llvm::Triple triple) {
   case llvm::Triple::WASI:
     addPlatformConditionValue(PlatformConditionKind::OS, "WASI");
     break;
+  case llvm::Triple::UnknownOS:
+    if (Target.getOSName() == "none") {
+      addPlatformConditionValue(PlatformConditionKind::OS, "none");
+      break;
+    }
+    LLVM_FALLTHROUGH;
   default:
     UnsupportedOS = true;
     break;
diff --git a/lib/Basic/Platform.cpp b/lib/Basic/Platform.cpp
index 3c91d7f7d3b99..274a587e99803 100644
--- a/lib/Basic/Platform.cpp
+++ b/lib/Basic/Platform.cpp
@@ -175,8 +175,6 @@ static StringRef getPlatformNameForDarwin(const DarwinPlatformKind platform) {
 
 StringRef swift::getPlatformNameForTriple(const llvm::Triple &triple) {
   switch (triple.getOS()) {
-  case llvm::Triple::UnknownOS:
-    llvm_unreachable("unknown OS");
   case llvm::Triple::ZOS:
   case llvm::Triple::Ananas:
   case llvm::Triple::CloudABI:
@@ -234,6 +232,8 @@ StringRef swift::getPlatformNameForTriple(const llvm::Triple &triple) {
     return "haiku";
   case llvm::Triple::WASI:
     return "wasi";
+  case llvm::Triple::UnknownOS:
+    return "none";
   }
   llvm_unreachable("unsupported OS");
 }
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 4b3e384315fdb..bab897c8b4e89 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -368,6 +368,8 @@ Driver::buildToolChain(const llvm::opt::InputArgList &ArgList) {
     return std::make_unique<toolchains::GenericUnix>(*this, target);
   case llvm::Triple::WASI:
     return std::make_unique<toolchains::GenericUnix>(*this, target);
+  case llvm::Triple::UnknownOS:
+    return std::make_unique<toolchains::GenericUnix>(*this, target);
   default:
     Diags.diagnose(SourceLoc(), diag::error_unknown_target,
                    ArgList.getLastArg(options::OPT_target)->getValue());
diff --git a/test/Driver/baremetal-target.swift b/test/Driver/baremetal-target.swift
new file mode 100644
index 0000000000000..25f292954a1c4
--- /dev/null
+++ b/test/Driver/baremetal-target.swift
@@ -0,0 +1,4 @@
+// RUN: %swiftc_driver_plain -target aarch64-unknwon-none-none -driver-print-jobs %s 2>&1 | %FileCheck %s
+
+// CHECK: {{.*}}swift{{c|-frontend}}{{(.exe)?"?}} -frontend -c
+// CHECK: {{.*}}clang{{(.exe)?"?}} -fuse-ld=gold
diff --git a/test/Driver/options.swift b/test/Driver/options.swift
index 130eb959bf901..69de3189ad6f3 100644
--- a/test/Driver/options.swift
+++ b/test/Driver/options.swift
@@ -80,8 +80,8 @@
 // RUN: %swift_driver -g -### %s 2>&1 | %FileCheck -check-prefix=OPTIONS_BEFORE_FILE %s
 // OPTIONS_BEFORE_FILE: -g
 
-// RUN: not %swift_driver -target abc -### %s 2>&1 | %FileCheck -check-prefix=BAD_TARGET %s
-// BAD_TARGET: error: unknown target 'abc'
+// RUN: not %swiftc_driver_plain -target x86_64-unknown-hurd -### %s 2>&1 | %FileCheck -check-prefix=BAD_TARGET %s
+// BAD_TARGET: error: unknown target 'x86_64-unknown-hurd'
 
 // RUN: %swiftc_driver -incremental %s -### 2>&1 | %FileCheck -check-prefix=INCREMENTAL_WITHOUT_OFM %s
 // INCREMENTAL_WITHOUT_OFM: warning: ignoring -incremental (currently requires an output file map)