diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index b34f0b41ff..b34fe33fcb 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -138,18 +138,18 @@ typedef int clockid_t;
 #undef stat
 #undef fstat
 #ifdef RUBY_EXPORT
-#define utime(_p, _t)		rb_w32_utime(_p, _t)
+#define utime(_p, _t)		rb_w32_uutime(_p, _t)
 #undef HAVE_UTIMES
 #define HAVE_UTIMES 1
-#define utimes(_p, _t)		rb_w32_utimes(_p, _t)
+#define utimes(_p, _t)		rb_w32_uutimes(_p, _t)
 #undef HAVE_UTIMENSAT
 #define HAVE_UTIMENSAT 1
 #define AT_FDCWD		-100
-#define utimensat(_d, _p, _t, _f)	rb_w32_utimensat(_d, _p, _t, _f)
+#define utimensat(_d, _p, _t, _f)	rb_w32_uutimensat(_d, _p, _t, _f)
 #define lseek(_f, _o, _w)	rb_w32_lseek(_f, _o, _w)
 
 #define pipe(p)			rb_w32_pipe(p)
-#define open			rb_w32_open
+#define open			rb_w32_uopen
 #define close(h)		rb_w32_close(h)
 #define fclose(f)		rb_w32_fclose(f)
 #define read(f, b, s)		rb_w32_read(f, b, s)
@@ -165,11 +165,11 @@ typedef int clockid_t;
 #define isatty(h)		rb_w32_isatty(h)
 
 #undef mkdir
-#define mkdir(p, m)		rb_w32_mkdir(p, m)
+#define mkdir(p, m)		rb_w32_umkdir(p, m)
 #undef rmdir
-#define rmdir(p)		rb_w32_rmdir(p)
+#define rmdir(p)		rb_w32_urmdir(p)
 #undef unlink
-#define unlink(p)		rb_w32_unlink(p)
+#define unlink(p)		rb_w32_uunlink(p)
 #endif /* RUBY_EXPORT */
 
 /* same with stati64 except the size of st_ino and nanosecond timestamps */
@@ -200,9 +200,9 @@ struct stati128 {
 #define HAVE_STRUCT_STAT_ST_MTIMENSEC
 #define HAVE_STRUCT_STAT_ST_CTIMENSEC
 #define fstat(fd,st)		rb_w32_fstati128(fd,st)
-#define stati128(path, st)	rb_w32_stati128(path,st)
-#define lstat(path,st)		rb_w32_lstati128(path,st)
-#define access(path,mode)	rb_w32_access(path,mode)
+#define stati128(path, st)	rb_w32_ustati128(path,st)
+#define lstat(path,st)		rb_w32_ulstati128(path,st)
+#define access(path,mode)	rb_w32_uaccess(path,mode)
 
 #define strcasecmp		_stricmp
 #define strncasecmp		_strnicmp
@@ -287,6 +287,7 @@ extern int    socketpair(int, int, int, int *);
 extern int    getifaddrs(struct ifaddrs **);
 extern void   freeifaddrs(struct ifaddrs *);
 extern char * rb_w32_getcwd(char *, int);
+extern char * rb_w32_ugetcwd(char *, int);
 extern char * rb_w32_ugetenv(const char *);
 extern char * rb_w32_getenv(const char *);
 extern int    rb_w32_rename(const char *, const char *);
@@ -433,11 +434,7 @@ extern int rb_w32_utruncate(const char *path, off_t length);
 
 #undef HAVE_TRUNCATE
 #define HAVE_TRUNCATE 1
-#if defined HAVE_TRUNCATE64
-#define truncate truncate64
-#else
-#define truncate rb_w32_truncate
-#endif
+#define truncate rb_w32_utruncate
 
 #if defined(_MSC_VER) && _MSC_VER >= 1400 && _MSC_VER < 1800
 #define strtoll  _strtoi64
@@ -706,13 +703,13 @@ extern char *rb_w32_strerror(int);
 #define get_osfhandle(h)	rb_w32_get_osfhandle(h)
 
 #undef getcwd
-#define getcwd(b, s)		rb_w32_getcwd(b, s)
+#define getcwd(b, s)		rb_w32_ugetcwd(b, s)
 
 #undef getenv
 #define getenv(n)		rb_w32_ugetenv(n)
 
 #undef rename
-#define rename(o, n)		rb_w32_rename(o, n)
+#define rename(o, n)		rb_w32_urename(o, n)
 
 #undef times
 #define times(t)		rb_w32_times(t)
diff --git a/localeinit.c b/localeinit.c
index bec29a6d46..bbcbac832e 100644
--- a/localeinit.c
+++ b/localeinit.c
@@ -123,8 +123,9 @@ Init_enc_set_filesystem_encoding(void)
     idx = ENCINDEX_US_ASCII;
 #elif defined _WIN32
     char cp[SIZEOF_CP_NAME];
-    const UINT codepage = ruby_w32_codepage[1] ? ruby_w32_codepage[1] :
-	AreFileApisANSI() ? GetACP() : GetOEMCP();
+    const UINT codepage = ruby_w32_codepage[1];
+    if (!codepage) return ENCINDEX_UTF_8;
+    /* for debugging */
     CP_FORMAT(cp, codepage);
     idx = rb_enc_find_index(cp);
     if (idx < 0) idx = ENCINDEX_ASCII;
diff --git a/test/ruby/test_dir_m17n.rb b/test/ruby/test_dir_m17n.rb
index c2c0c4999e..67bad8a514 100644
--- a/test/ruby/test_dir_m17n.rb
+++ b/test/ruby/test_dir_m17n.rb
@@ -17,27 +17,19 @@ class TestDir_M17N < Test::Unit::TestCase
       assert_separately(["-E#{encoding}"], <<-EOS, :chdir=>dir)
         filename = #{code}.chr('UTF-8').force_encoding("#{encoding}")
         File.open(filename, "w") {}
-        opts = {:encoding => Encoding.default_external} if /mswin|mingw/ =~ RUBY_PLATFORM
-        ents = Dir.entries(".", **(opts||{}))
+        ents = Dir.entries(".")
+        if /mswin|mingw/ =~ RUBY_PLATFORM
+          filename = filename.encode("UTF-8")
+        end
         assert_include(ents, filename)
       EOS
 
       return if /cygwin/ =~ RUBY_PLATFORM
       assert_separately(%w[-EASCII-8BIT], <<-EOS, :chdir=>dir)
         filename = #{code}.chr('UTF-8').force_encoding("ASCII-8BIT")
-        opts = {:encoding => Encoding.default_external} if /mswin|mingw/ =~ RUBY_PLATFORM
-        ents = Dir.entries(".", **(opts||{}))
-        expected_filename = #{code}.chr('UTF-8').encode(Encoding.find("filesystem")) rescue expected_filename = "?"
-        expected_filename = expected_filename.force_encoding("ASCII-8BIT")
+        ents = Dir.entries(".")
         if /mswin|mingw/ =~ RUBY_PLATFORM
-          case
-          when ents.include?(filename)
-          when ents.include?(expected_filename)
-            filename = expected_filename
-          else
-            ents = Dir.entries(".", :encoding => Encoding.find("filesystem"))
-            filename = expected_filename
-          end
+          filename.force_encoding("UTF-8")
         end
         assert_include(ents, filename)
       EOS
@@ -199,27 +191,23 @@ class TestDir_M17N < Test::Unit::TestCase
       assert_separately(%w[-EEUC-JP], <<-'EOS', :chdir=>d)
         filename = "\xA4\xA2".force_encoding("euc-jp")
         File.open(filename, "w") {}
-        opts = {:encoding => Encoding.default_external} if /mswin|mingw/ =~ RUBY_PLATFORM
-        ents = Dir.entries(".", **(opts||{}))
+        ents = Dir.entries(".")
         if /darwin/ =~ RUBY_PLATFORM
           filename = filename.encode("utf-8").force_encoding("euc-jp")
+        elsif /mswin|mingw/ =~ RUBY_PLATFORM
+          filename = filename.encode("utf-8")
         end
         assert_include(ents, filename)
       EOS
       assert_separately(%w[-EASCII-8BIT], <<-'EOS', :chdir=>d)
         filename = "\xA4\xA2".force_encoding('ASCII-8BIT')
-        win_expected_filename = filename.encode(Encoding.find("filesystem"), "euc-jp") rescue "?"
-        opts = {:encoding => Encoding.default_external} if /mswin|mingw/ =~ RUBY_PLATFORM
-        ents = Dir.entries(".", **(opts||{}))
+        ents = Dir.entries(".")
         unless ents.include?(filename)
           case RUBY_PLATFORM
           when /darwin/
             filename = filename.encode("utf-8", "euc-jp").b
           when /mswin|mingw/
-            if ents.include?(win_expected_filename.b)
-              ents = Dir.entries(".", :encoding => Encoding.find("filesystem"))
-              filename = win_expected_filename
-            end
+            filename = filename.encode("utf-8", "euc-jp")
           end
         end
         assert_include(ents, filename)
@@ -414,13 +402,8 @@ class TestDir_M17N < Test::Unit::TestCase
       orig.each {|n| open(n, "w") {}}
       enc = Encoding.find("filesystem")
       enc = Encoding::ASCII_8BIT if enc == Encoding::US_ASCII
-      if /mswin|mingw/ =~ RUBY_PLATFORM
-        opts = {:encoding => enc}
-        orig.map! {|o| o.encode("filesystem") rescue o.tr("^a-z", "?")}
-      else
-        orig.each {|o| o.force_encoding(enc) }
-      end
-      ents = Dir.entries(".", **(opts||{})).reject {|n| /\A\./ =~ n}
+      orig.each {|o| o.force_encoding(enc) }
+      ents = Dir.entries(".").reject {|n| /\A\./ =~ n}
       ents.sort!
       PP.assert_equal(orig, ents, bug7267)
     }
@@ -431,13 +414,9 @@ class TestDir_M17N < Test::Unit::TestCase
     expected = []
     results = []
     orig.each {|o|
-      if /mswin|mingw/ =~ RUBY_PLATFORM
-        n = (o.encode("filesystem") rescue next)
-      else
-        enc = Encoding.find("filesystem")
-        enc = Encoding::ASCII_8BIT if enc == Encoding::US_ASCII
-        n = o.dup.force_encoding(enc)
-      end
+      enc = Encoding.find("filesystem")
+      enc = Encoding::ASCII_8BIT if enc == Encoding::US_ASCII
+      n = o.dup.force_encoding(enc)
       expected << n
       with_tmpdir {
         Dir.mkdir(o)
diff --git a/win32/dir.h b/win32/dir.h
index a0759804f6..28fbb6cf2e 100644
--- a/win32/dir.h
+++ b/win32/dir.h
@@ -38,11 +38,12 @@ void           rb_w32_rewinddir(DIR *);
 void           rb_w32_closedir(DIR *);
 char          *rb_w32_ugetcwd(char *, int);
 
-#define opendir(s)   rb_w32_opendir((s))
+#define opendir(s)   rb_w32_uopendir((s))
 #define readdir(d)   rb_w32_readdir((d), 0)
 #define telldir(d)   rb_w32_telldir((d))
 #define seekdir(d, l)   rb_w32_seekdir((d), (l))
 #define rewinddir(d) rb_w32_rewinddir((d))
 #define closedir(d)  rb_w32_closedir((d))
+#define getcwd(b, s) rb_w32_ugetcwd(b, s)
 
 #endif /* RUBY_WIN32_DIR_H */
diff --git a/win32/file.c b/win32/file.c
index 71320242e2..5c34bd42b4 100644
--- a/win32/file.c
+++ b/win32/file.c
@@ -347,7 +347,7 @@ rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_na
 	if (path_cp == INVALID_CODE_PAGE || rb_enc_str_asciionly_p(path)) {
 	    /* use filesystem encoding if expanding home dir */
 	    path_encoding = rb_filesystem_encoding();
-	    cp = path_cp = system_code_page();
+	    cp = path_cp = code_page(path_encoding);
 	}
 
 	/* ignores dir since we are expanding home */
diff --git a/win32/win32.c b/win32/win32.c
index 59040824ad..4f0c0d29c1 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -2270,7 +2270,7 @@ rb_w32_conv_from_wstr(const WCHAR *wstr, long *lenp, rb_encoding *enc)
     long len;
     char *ptr;
 
-    if (NIL_P(str)) return wstr_to_filecp(wstr, lenp);
+    if (NIL_P(str)) return wstr_to_utf8(wstr, lenp);
     *lenp = len = RSTRING_LEN(str);
     memcpy(ptr = malloc(len + 1), RSTRING_PTR(str), len);
     ptr[len] = '\0';