Index: dir.c
===================================================================
--- dir.c	(revision 24594)
+++ dir.c	(working copy)
@@ -892,6 +892,14 @@
 #define dir_s_chroot rb_f_notimplement
 #endif
 
+#ifndef pi_mkdir
+static int dir_s_mkdir_internal(VALUE path, int mode)
+{
+	return mkdir(RSTRING_PTR(path), mode);
+}
+#define pi_mkdir(path, mode)	dir_s_mkdir_internal(path, mode)
+#endif
+
 /*
  *  call-seq:
  *     Dir.mkdir( string [, integer] ) => 0
@@ -919,7 +927,7 @@
     }
 
     check_dirname(&path);
-    if (mkdir(RSTRING_PTR(path), mode) == -1)
+    if (pi_mkdir(path, mode) == -1)
 	rb_sys_fail(RSTRING_PTR(path));
 
     return INT2FIX(0);
Index: include/ruby/win32.h
===================================================================
--- include/ruby/win32.h	(revision 24594)
+++ include/ruby/win32.h	(working copy)
@@ -164,8 +164,8 @@
 #define isatty(h)		rb_w32_isatty(h)
 #endif
 
-#undef mkdir
-#define mkdir(p, m)		rb_w32_mkdir(p, m)
+#undef pi_mkdir
+#define pi_mkdir(p, m)		rb_w32_mkdir(p, m)
 #undef rmdir
 #define rmdir(p)		rb_w32_rmdir(p)
 #undef unlink
@@ -273,7 +273,7 @@
 #if !defined(__BORLANDC__)
 extern int rb_w32_isatty(int);
 #endif
-extern int rb_w32_mkdir(const char *, int);
+extern int rb_w32_mkdir(unsigned long, int);
 extern int rb_w32_rmdir(const char *);
 extern int rb_w32_unlink(const char *);
 extern int rb_w32_stati64(const char *, struct stati64 *);
@@ -577,4 +577,4 @@
 }  /* extern "C" { */
 #endif
 
-#endif /* RUBY_WIN32_H */
+#endif /* RUBY_WIN32_H */
\ No newline at end of file
Index: win32/win32.c
===================================================================
--- win32/win32.c	(revision 24594)
+++ win32/win32.c	(working copy)
@@ -569,6 +569,20 @@
     NtSocketsInitialized = 1;
 }
 
+static rb_encoding *
+w32_utf16(void)
+{
+	static rb_encoding *w32_utf16 = (rb_encoding *)-1;
+
+    if (w32_utf16 == (rb_encoding *)-1) {
+        w32_utf16 = rb_enc_find("UTF-16LE");
+        if (w32_utf16 == rb_ascii8bit_encoding())
+            w32_utf16 = NULL;
+    }
+
+	return w32_utf16;
+}
+
 //
 // Initialization stuff
 //
@@ -5115,19 +5129,36 @@
 }
 
 int
-rb_w32_mkdir(const char *path, int mode)
-{
+rb_w32_mkdir(VALUE path, int mode)
+{ 
     int ret = -1;
-    RUBY_CRITICAL(do {
-	if (CreateDirectory(path, NULL) == FALSE) {
-	    errno = map_errno(GetLastError());
-	    break;
-	}
-	if (chmod(path, mode) == -1) {
-	    RemoveDirectory(path);
-	    break;
-	}
-	ret = 0;
+
+	RUBY_CRITICAL(do {
+		if (w32_utf16()) {
+			VALUE wpath = rb_str_encode(path, rb_enc_from_encoding(w32_utf16()), 0,
+						 Qnil);
+			rb_enc_str_buf_cat(wpath, "", 1, w32_utf16()); /* workaround */
+
+			if (CreateDirectoryW((WCHAR*) RSTRING_PTR(wpath), NULL) == FALSE) {
+				errno = map_errno(GetLastError());
+				break;
+			}
+			if (_wchmod((WCHAR*) RSTRING_PTR(wpath), mode) == -1) {
+				RemoveDirectoryW((WCHAR*) RSTRING_PTR(wpath));
+				break;
+			}
+		}
+		else {
+			if (CreateDirectory(RSTRING_PTR(path), NULL) == FALSE) {
+				errno = map_errno(GetLastError());
+				break;
+			}
+			if (chmod(RSTRING_PTR(path), mode) == -1) {
+				RemoveDirectory(RSTRING_PTR(path));
+				break;
+			}
+		}
+		ret = 0;
     } while (0));
     return ret;
 }