diff --git a/lib/pure/os.nim b/lib/pure/os.nim
index 43bdb16eed..8868233502 100644
--- a/lib/pure/os.nim
+++ b/lib/pure/os.nim
@@ -544,33 +544,31 @@ proc SplitPath*(path: string): tuple[head, tail: string] {.
     result.head = ""
     result.tail = path
 
+proc parentDirPos(path: string): int =
+  var q = 1
+  if path[len(path)-1] in {dirsep, altsep}: q = 2
+  for i in countdown(len(path)-q, 0):
+    if path[i] in {dirsep, altsep}: return i
+  result = -1
+
 proc parentDir*(path: string): string {.
   noSideEffect, rtl, extern: "nos$1".} =
   ## Returns the parent directory of `path`.
   ##
   ## This is often the same as the ``head`` result of ``splitPath``.
-  ## If there is no parent, ``path`` is returned.
+  ## If there is no parent, "" is returned.
   ## | Example: ``parentDir("/usr/local/bin") == "/usr/local"``.
   ## | Example: ``parentDir("/usr/local/bin/") == "/usr/local"``.
-  var
-    sepPos = -1
-    q = 1
-  if path[len(path)-1] in {dirsep, altsep}:
-    q = 2
-  for i in countdown(len(path)-q, 0):
-    if path[i] in {dirsep, altsep}:
-      sepPos = i
-      break
+  let sepPos = parentDirPos(path)
   if sepPos >= 0:
     result = substr(path, 0, sepPos-1)
   else:
-    result = path
+    result = ""
 
 proc isRootDir*(path: string): bool {.
   noSideEffect, rtl, extern: "nos$1".} =
   ## Checks whether a given `path` is a root directory 
-  var p = parentDir(path)
-  result = p == path or p.len == 0
+  result = parentDirPos(path) < 0
 
 iterator parentDirs*(path: string, fromRoot=false, inclusive=true): string =
   ## Walks over all parent directories of a given `path`
@@ -591,14 +589,20 @@ iterator parentDirs*(path: string, fromRoot=false, inclusive=true): string =
   else:
     for i in countup(0, path.len - 2): # ignore the last /
       # deal with non-normalized paths such as /foo//bar//baz
-      if path[i] in {dirsep, altsep} and (i == 0 or path[i-1] notin {dirsep, altsep}):
+      if path[i] in {dirsep, altsep} and 
+          (i == 0 or path[i-1] notin {dirsep, altsep}):
         yield path.substr(0, i)
 
     if inclusive: yield path
 
 proc `/../` * (head, tail: string): string {.noSideEffect.} =
-  ## The same as ``parentDir(head) / tail``
-  return parentDir(head) / tail
+  ## The same as ``parentDir(head) / tail`` unless there is no parent directory.
+  ## Then ``head / tail`` is performed instead.
+  let sepPos = parentDirPos(path)
+  if sepPos >= 0:
+    result = substr(path, 0, sepPos-1) / tail
+  else:
+    result = path / tail
 
 proc normExt(ext: string): string =
   if ext == "" or ext[0] == extSep: result = ext # no copy needed here
diff --git a/web/news.txt b/web/news.txt
index 32eab8c59f..1b492fa971 100644
--- a/web/news.txt
+++ b/web/news.txt
@@ -27,6 +27,7 @@ Changes affecting backwards compatibility
   name but which take different parameters have been introduced. These procs now
   require an error code to be passed to them. This error code can be retrieved
   using the new ``OSLastError`` proc.
+- ``os.parentDir`` now returns "" if there is no parent dir.
 
 
 Compiler Additions