diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d752108797d..b6ae0e5ffab 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,16 @@
+2018-08-28  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/87116
+	* src/filesystem/std-path.cc (path::lexically_normal): When handling
+	a dot-dot filename, preserve an empty final component in the iteration
+	sequence.
+	[_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Use preferred-separator for
+	root-directory.
+	* testsuite/27_io/filesystem/path/generation/normal.cc: Add new tests
+	for more than two adjacent dot-dot filenames.
+	[_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Replace slashes with
+	preferred-separator in expected normalized strings.
+
 2018-08-25  Iain Sandoe  <iain@sandoe.co.uk>
 
 	PR libstdc++/70694
diff --git a/libstdc++-v3/src/filesystem/std-path.cc b/libstdc++-v3/src/filesystem/std-path.cc
index f6c0b8bb0f6..f382eb3759a 100644
--- a/libstdc++-v3/src/filesystem/std-path.cc
+++ b/libstdc++-v3/src/filesystem/std-path.cc
@@ -438,7 +438,7 @@ path::lexically_normal() const
     {
 #ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
       // Replace each slash character in the root-name
-      if (p._M_type == _Type::_Root_name)
+      if (p._M_type == _Type::_Root_name || p._M_type == _Type::_Root_dir)
 	{
 	  string_type s = p.native();
 	  std::replace(s.begin(), s.end(), L'/', L'\\');
@@ -458,7 +458,8 @@ path::lexically_normal() const
 	    }
 	  else if (!ret.has_relative_path())
 	    {
-	      if (!ret.is_absolute())
+	      // remove a dot-dot filename immediately after root-directory
+	      if (!ret.has_root_directory())
 		ret /= p;
 	    }
 	  else
@@ -471,8 +472,18 @@ path::lexically_normal() const
 		{
 		  // Remove the filename before the trailing slash
 		  // (equiv. to ret = ret.parent_path().remove_filename())
-		  ret._M_pathname.erase(elem._M_cur->_M_pos);
-		  ret._M_cmpts.erase(elem._M_cur, ret._M_cmpts.end());
+
+		  if (elem == ret.begin())
+		    ret.clear();
+		  else
+		    {
+		      ret._M_pathname.erase(elem._M_cur->_M_pos);
+		      // Do we still have a trailing slash?
+		      if (std::prev(elem)->_M_type == _Type::_Filename)
+			ret._M_cmpts.erase(elem._M_cur);
+		      else
+			ret._M_cmpts.erase(elem._M_cur, ret._M_cmpts.end());
+		    }
 		}
 	      else // ???
 		ret /= p;
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/generation/normal.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/generation/normal.cc
index 6d0e2007a75..3b8311f81ad 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/path/generation/normal.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/generation/normal.cc
@@ -24,7 +24,17 @@
 #include <testsuite_hooks.h>
 
 using std::filesystem::path;
-using __gnu_test::compare_paths;
+
+void
+compare_paths(path p, std::string expected)
+{
+#if defined(_WIN32) && !defined(__CYGWIN__)
+  for (auto& c : expected)
+    if (c == '/')
+      c = '\\';
+#endif
+  __gnu_test::compare_paths(p, expected);
+}
 
 void
 test01()
@@ -69,8 +79,11 @@ test03()
     {"/foo"        , "/foo" },
     {"/foo/"       , "/foo/" },
     {"/foo/."      , "/foo/" },
-    {"/foo/bar/.." , "/foo/" },
     {"/foo/.."     , "/" },
+    {"/foo/../.."  , "/" },
+    {"/foo/bar/.." , "/foo/" },
+    {"/foo/bar/../.." , "/" },
+    {"/foo/bar/baz/../../.." , "/" }, // PR libstdc++/87116
 
     {"/."          , "/" },
     {"/./"         , "/" },
@@ -88,10 +101,11 @@ test03()
     {"foo/.."      , "." },
     {"foo/../"     , "." },
     {"foo/../.."   , ".." },
+    {"foo/../../..", "../.." },
 
     // with root name (OS-dependent):
 #if defined(_WIN32) && !defined(__CYGWIN__)
-    {"C:bar/.."    , "C:." },
+    {"C:bar/.."    , "C:" },
 #else
     {"C:bar/.."    , "." },
 #endif
@@ -119,10 +133,53 @@ test03()
     compare_paths( path(test.input).lexically_normal(), test.normalized );
 }
 
+void
+test04()
+{
+  // PR libstdc++/87116
+  path p = "a/b/c";
+  compare_paths( (p/"../..").lexically_normal(), "a/" );
+
+  p = "a/b/c/d/e";
+  compare_paths( (p/"..").lexically_normal(),  "a/b/c/d/" );
+  compare_paths( (p/"../..").lexically_normal(),  "a/b/c/" );
+  compare_paths( (p/"../../..").lexically_normal(),  "a/b/" );
+  compare_paths( (p/"../../../..").lexically_normal(),  "a/" );
+  compare_paths( (p/"../../../../..").lexically_normal(),  "." );
+  compare_paths( (p/"../../../../../..").lexically_normal(),  ".." );
+
+  p = "/a/b/c/d/e";
+  compare_paths( (p/"..").lexically_normal(),  "/a/b/c/d/" );
+  compare_paths( (p/"../..").lexically_normal(),  "/a/b/c/" );
+  compare_paths( (p/"../../..").lexically_normal(),  "/a/b/" );
+  compare_paths( (p/"../../../..").lexically_normal(),  "/a/" );
+  compare_paths( (p/"../../../../..").lexically_normal(),  "/" );
+  compare_paths( (p/"../../../../../..").lexically_normal(),  "/" );
+
+#if defined(_WIN32) && !defined(__CYGWIN__)
+  p = "A:b/c/d/e";
+  compare_paths( (p/"..").lexically_normal(),  "A:b/c/d/" );
+  compare_paths( (p/"../..").lexically_normal(),  "A:b/c/" );
+  compare_paths( (p/"../../..").lexically_normal(),  "A:b/" );
+  compare_paths( (p/"../../../..").lexically_normal(),  "A:" );
+  compare_paths( (p/"../../../../..").lexically_normal(),  "A:.." );
+  compare_paths( (p/"../../../../../..").lexically_normal(),  "A:../.." );
+
+  p = "A:/b/c/d/e";
+  compare_paths( (p/"..").lexically_normal(),  "A:/b/c/d/" );
+  compare_paths( (p/"../..").lexically_normal(),  "A:/b/c/" );
+  compare_paths( (p/"../../..").lexically_normal(),  "A:/b/" );
+  compare_paths( (p/"../../../..").lexically_normal(),  "A:/" );
+  compare_paths( (p/"../../../../..").lexically_normal(),  "A:/" );
+  compare_paths( (p/"../../../../../..").lexically_normal(),  "A:/" );
+#endif
+}
+
 int
 main()
 {
   test01();
   test02();
   test03();
+  test04();
 }