diff --git a/lib/Support/PathV2.cpp b/lib/Support/PathV2.cpp
index e360e9cd1fe..47e59dd1cf1 100644
--- a/lib/Support/PathV2.cpp
+++ b/lib/Support/PathV2.cpp
@@ -574,6 +574,22 @@ error_code stem(const StringRef &path, StringRef &result) {
   return make_error_code(errc::success);
 }
 
+error_code extension(const StringRef &path, StringRef &result) {
+  StringRef fname;
+  if (error_code ec = filename(path, fname)) return ec;
+  size_t pos = fname.find_last_of('.');
+  if (pos == StringRef::npos)
+    result = StringRef();
+  else
+    if ((fname.size() == 1 && fname == ".") ||
+        (fname.size() == 2 && fname == ".."))
+      result = StringRef();
+    else
+      result = StringRef(fname.begin() + pos, fname.size() - pos);
+
+  return make_error_code(errc::success);
+}
+
 }
 }
 }
diff --git a/unittests/Support/Path.cpp b/unittests/Support/Path.cpp
index 70cf213f191..2114a181fa1 100644
--- a/unittests/Support/Path.cpp
+++ b/unittests/Support/Path.cpp
@@ -100,6 +100,9 @@ TEST(Support, Path) {
     if (error_code ec = sys::path::stem(*i, res))
       ASSERT_FALSE(ec.message().c_str());
     outs() << "    stem: " << res << '\n';
+    if (error_code ec = sys::path::extension(*i, res))
+      ASSERT_FALSE(ec.message().c_str());
+    outs() << "    stem: " << res << '\n';
 
     temp_store = *i;
     if (error_code ec = sys::path::make_absolute(temp_store))
@@ -113,10 +116,17 @@ TEST(Support, Path) {
     if (error_code ec = sys::path::replace_extension(temp_store, "ext"))
       ASSERT_FALSE(ec.message().c_str());
     outs() << "    replace_extension: " << temp_store << '\n';
+    StringRef stem, ext;
     if (error_code ec = sys::path::stem(
-      StringRef(temp_store.begin(), temp_store.size()), res))
+      StringRef(temp_store.begin(), temp_store.size()), stem))
       ASSERT_FALSE(ec.message().c_str());
-    outs() << "    stem: " << res << '\n';
+    outs() << "    stem: " << stem << '\n';
+    if (error_code ec = sys::path::extension(
+      StringRef(temp_store.begin(), temp_store.size()), ext))
+      ASSERT_FALSE(ec.message().c_str());
+    outs() << "    extension: " << ext << '\n';
+    EXPECT_EQ(*(--sys::path::end(
+      StringRef(temp_store.begin(), temp_store.size()))), (stem + ext).str());
     if (error_code ec = sys::path::native(*i, temp_store))
       ASSERT_FALSE(ec.message().c_str());
     outs() << "    native: " << temp_store << '\n';