diff --git a/src/liblibc/lib.rs b/src/liblibc/lib.rs
index 731c46d6f4d50..cf80d5a06d5f4 100644
--- a/src/liblibc/lib.rs
+++ b/src/liblibc/lib.rs
@@ -208,7 +208,7 @@ pub use funcs::bsd43::{shutdown};
 #[cfg(windows)] pub use consts::os::extra::{TRUE, FALSE, INFINITE};
 #[cfg(windows)] pub use consts::os::extra::{PROCESS_TERMINATE, PROCESS_QUERY_INFORMATION};
 #[cfg(windows)] pub use consts::os::extra::{STILL_ACTIVE, DETACHED_PROCESS};
-#[cfg(windows)] pub use consts::os::extra::{CREATE_NEW_PROCESS_GROUP};
+#[cfg(windows)] pub use consts::os::extra::{CREATE_NEW_PROCESS_GROUP, CREATE_UNICODE_ENVIRONMENT};
 #[cfg(windows)] pub use consts::os::extra::{FILE_BEGIN, FILE_END, FILE_CURRENT};
 #[cfg(windows)] pub use consts::os::extra::{FILE_GENERIC_READ, FILE_GENERIC_WRITE};
 #[cfg(windows)] pub use consts::os::extra::{FILE_SHARE_READ, FILE_SHARE_WRITE, FILE_SHARE_DELETE};
@@ -1937,6 +1937,7 @@ pub mod consts {
 
             pub static DETACHED_PROCESS: DWORD = 0x00000008;
             pub static CREATE_NEW_PROCESS_GROUP: DWORD = 0x00000200;
+            pub static CREATE_UNICODE_ENVIRONMENT: DWORD = 0x00000400;
 
             pub static PIPE_ACCESS_DUPLEX: DWORD = 0x00000003;
             pub static PIPE_ACCESS_INBOUND: DWORD = 0x00000001;
@@ -4193,7 +4194,7 @@ pub mod funcs {
         pub mod kernel32 {
             use types::os::arch::c95::{c_uint};
             use types::os::arch::extra::{BOOL, DWORD, SIZE_T, HMODULE,
-                                               LPCWSTR, LPWSTR, LPCSTR, LPSTR,
+                                               LPCWSTR, LPWSTR,
                                                LPCH, LPDWORD, LPVOID,
                                                LPCVOID, LPOVERLAPPED,
                                                LPSECURITY_ATTRIBUTES,
@@ -4251,8 +4252,8 @@ pub mod funcs {
                                    dwProcessId: DWORD)
                                    -> HANDLE;
                 pub fn GetCurrentProcess() -> HANDLE;
-                pub fn CreateProcessA(lpApplicationName: LPCSTR,
-                                      lpCommandLine: LPSTR,
+                pub fn CreateProcessW(lpApplicationName: LPCWSTR,
+                                      lpCommandLine: LPWSTR,
                                       lpProcessAttributes:
                                       LPSECURITY_ATTRIBUTES,
                                       lpThreadAttributes:
@@ -4260,7 +4261,7 @@ pub mod funcs {
                                       bInheritHandles: BOOL,
                                       dwCreationFlags: DWORD,
                                       lpEnvironment: LPVOID,
-                                      lpCurrentDirectory: LPCSTR,
+                                      lpCurrentDirectory: LPCWSTR,
                                       lpStartupInfo: LPSTARTUPINFO,
                                       lpProcessInformation:
                                       LPPROCESS_INFORMATION)
diff --git a/src/libnative/io/process.rs b/src/libnative/io/process.rs
index 81c76bba7a0eb..dbb191911e741 100644
--- a/src/libnative/io/process.rs
+++ b/src/libnative/io/process.rs
@@ -258,7 +258,7 @@ fn spawn_process_os(config: p::ProcessConfig,
         GetCurrentProcess,
         DuplicateHandle,
         CloseHandle,
-        CreateProcessA
+        CreateProcessW
     };
     use libc::funcs::extra::msvcrt::get_osfhandle;
 
@@ -318,15 +318,15 @@ fn spawn_process_os(config: p::ProcessConfig,
         let mut create_err = None;
 
         // stolen from the libuv code.
-        let mut flags = 0;
+        let mut flags = libc::CREATE_UNICODE_ENVIRONMENT;
         if config.detach {
             flags |= libc::DETACHED_PROCESS | libc::CREATE_NEW_PROCESS_GROUP;
         }
 
         with_envp(env, |envp| {
             with_dirp(dir, |dirp| {
-                cmd.with_c_str(|cmdp| {
-                    let created = CreateProcessA(ptr::null(), mem::transmute(cmdp),
+                os::win32::as_mut_utf16_p(cmd, |cmdp| {
+                    let created = CreateProcessW(ptr::null(), cmdp,
                                                  ptr::mut_null(), ptr::mut_null(), TRUE,
                                                  flags, envp, dirp, &mut si,
                                                  &mut pi);
@@ -691,7 +691,7 @@ fn with_envp<T>(env: Option<~[(~str, ~str)]>, cb: |*mut c_void| -> T) -> T {
 
             for pair in env.iter() {
                 let kv = format!("{}={}", *pair.ref0(), *pair.ref1());
-                blk.push_all(kv.as_bytes());
+                blk.push_all(kv.to_utf16().as_slice());
                 blk.push(0);
             }
 
@@ -704,9 +704,12 @@ fn with_envp<T>(env: Option<~[(~str, ~str)]>, cb: |*mut c_void| -> T) -> T {
 }
 
 #[cfg(windows)]
-fn with_dirp<T>(d: Option<&Path>, cb: |*libc::c_char| -> T) -> T {
+fn with_dirp<T>(d: Option<&Path>, cb: |*u16| -> T) -> T {
     match d {
-      Some(dir) => dir.with_c_str(|buf| cb(buf)),
+      Some(dir) => match dir.as_str() {
+          Some(dir_str) => os::win32::as_utf16_p(dir_str, cb),
+          None => cb(ptr::null())
+      },
       None => cb(ptr::null())
     }
 }
diff --git a/src/libstd/os.rs b/src/libstd/os.rs
index f7324dc08b6d5..44c338a309180 100644
--- a/src/libstd/os.rs
+++ b/src/libstd/os.rs
@@ -141,10 +141,14 @@ pub mod win32 {
     }
 
     pub fn as_utf16_p<T>(s: &str, f: |*u16| -> T) -> T {
+        as_mut_utf16_p(s, |t| { f(t as *u16) })
+    }
+
+    pub fn as_mut_utf16_p<T>(s: &str, f: |*mut u16| -> T) -> T {
         let mut t = s.to_utf16();
         // Null terminate before passing on.
         t.push(0u16);
-        f(t.as_ptr())
+        f(t.as_mut_ptr())
     }
 }