diff --git a/lib/os.js b/lib/os.js
index cd4eb1c12f..4426612285 100644
--- a/lib/os.js
+++ b/lib/os.js
@@ -22,6 +22,9 @@ exports.platform = function() {
   return process.platform;
 };
 
+const trailingSlashRe = isWindows ? /[^:]\\$/
+                                  : /.\/$/;
+
 exports.tmpdir = function() {
   var path;
   if (isWindows) {
@@ -34,7 +37,7 @@ exports.tmpdir = function() {
            process.env.TEMP ||
            '/tmp';
   }
-  if (/[\\\/]$/.test(path))
+  if (trailingSlashRe.test(path))
     path = path.slice(0, -1);
   return path;
 };
diff --git a/test/parallel/test-os.js b/test/parallel/test-os.js
index b5f39973a6..dd1a1ae339 100644
--- a/test/parallel/test-os.js
+++ b/test/parallel/test-os.js
@@ -15,6 +15,12 @@ if (process.platform === 'win32') {
   assert.equal(os.tmpdir(), expected);
   process.env.TEMP = '\\temp\\';
   assert.equal(os.tmpdir(), '\\temp');
+  process.env.TEMP = '\\tmpdir/';
+  assert.equal(os.tmpdir(), '\\tmpdir/');
+  process.env.TEMP = '\\';
+  assert.equal(os.tmpdir(), '\\');
+  process.env.TEMP = 'C:\\';
+  assert.equal(os.tmpdir(), 'C:\\');
 } else {
   assert.equal(os.tmpdir(), '/tmpdir');
   process.env.TMPDIR = '';
@@ -25,6 +31,10 @@ if (process.platform === 'win32') {
   assert.equal(os.tmpdir(), '/tmp');
   process.env.TMPDIR = '/tmpdir/';
   assert.equal(os.tmpdir(), '/tmpdir');
+  process.env.TMPDIR = '/tmpdir\\';
+  assert.equal(os.tmpdir(), '/tmpdir\\');
+  process.env.TMPDIR = '/';
+  assert.equal(os.tmpdir(), '/');
 }
 
 var endianness = os.endianness();