diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index 7c2cd615303c0..b65e065fe9148 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -36,7 +36,6 @@ use sys::os as os_imp;
 ///
 /// * Current directory does not exist.
 /// * There are insufficient permissions to access the current directory.
-/// * The internal buffer is not large enough to hold the path.
 ///
 /// # Examples
 ///
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 334dd6b5f18c1..2b6b50a1a56d7 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -22,25 +22,17 @@ use io;
 use iter;
 use libc::{self, c_int, c_char, c_void};
 use mem;
-use ptr;
 use path::{self, PathBuf};
+use ptr;
 use slice;
 use str;
 use sys::c;
 use sys::fd;
 use vec;
 
-const BUF_BYTES: usize = 2048;
+const GETCWD_BUF_BYTES: usize = 2048;
 const TMPBUF_SZ: usize = 128;
 
-fn bytes2path(b: &[u8]) -> PathBuf {
-    PathBuf::from(<OsStr as OsStrExt>::from_bytes(b))
-}
-
-fn os2path(os: OsString) -> PathBuf {
-    bytes2path(os.as_bytes())
-}
-
 /// Returns the platform-specific value of errno
 pub fn errno() -> i32 {
     #[cfg(any(target_os = "macos",
@@ -102,12 +94,24 @@ pub fn error_string(errno: i32) -> String {
 }
 
 pub fn getcwd() -> io::Result<PathBuf> {
-    let mut buf = [0 as c_char; BUF_BYTES];
-    unsafe {
-        if libc::getcwd(buf.as_mut_ptr(), buf.len() as libc::size_t).is_null() {
-            Err(io::Error::last_os_error())
-        } else {
-            Ok(bytes2path(CStr::from_ptr(buf.as_ptr()).to_bytes()))
+    let mut buf = Vec::new();
+    let mut n = GETCWD_BUF_BYTES;
+    loop {
+        unsafe {
+            buf.reserve(n);
+            let ptr = buf.as_mut_ptr() as *mut libc::c_char;
+            if !libc::getcwd(ptr, buf.capacity() as libc::size_t).is_null() {
+                let len = CStr::from_ptr(buf.as_ptr() as *const libc::c_char).to_bytes().len();
+                buf.set_len(len);
+                buf.shrink_to_fit();
+                return Ok(PathBuf::from(OsString::from_vec(buf)));
+            } else {
+                let error = io::Error::last_os_error();
+                if error.raw_os_error() != Some(libc::ERANGE) {
+                    return Err(error);
+                }
+            }
+            n *= 2;
         }
     }
 }
@@ -129,11 +133,14 @@ pub struct SplitPaths<'a> {
 }
 
 pub fn split_paths<'a>(unparsed: &'a OsStr) -> SplitPaths<'a> {
+    fn bytes_to_path(b: &[u8]) -> PathBuf {
+        PathBuf::from(<OsStr as OsStrExt>::from_bytes(b))
+    }
     fn is_colon(b: &u8) -> bool { *b == b':' }
     let unparsed = unparsed.as_bytes();
     SplitPaths {
         iter: unparsed.split(is_colon as fn(&u8) -> bool)
-                      .map(bytes2path as fn(&'a [u8]) -> PathBuf)
+                      .map(bytes_to_path as fn(&'a [u8]) -> PathBuf)
     }
 }
 
@@ -444,7 +451,7 @@ pub fn page_size() -> usize {
 }
 
 pub fn temp_dir() -> PathBuf {
-    getenv("TMPDIR".as_ref()).map(os2path).unwrap_or_else(|| {
+    getenv("TMPDIR".as_ref()).map(PathBuf::from).unwrap_or_else(|| {
         if cfg!(target_os = "android") {
             PathBuf::from("/data/local/tmp")
         } else {
@@ -456,7 +463,7 @@ pub fn temp_dir() -> PathBuf {
 pub fn home_dir() -> Option<PathBuf> {
     return getenv("HOME".as_ref()).or_else(|| unsafe {
         fallback()
-    }).map(os2path);
+    }).map(PathBuf::from);
 
     #[cfg(any(target_os = "android",
               target_os = "ios"))]