diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index 77548f786..59c7bbe8d 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -590,7 +590,7 @@ mpz_mdiv(mrb_state *mrb, mpz_t *q, mpz_t *x, mpz_t *y)
     q->sn = 0;
   /* now if r != 0 and q < 0 we need to round q towards -inf */
   if (!uzero_p(&r) && qsign < 0)
-    mpz_sub_int(mrb, q, 1);
+    mpz_add_int(mrb, q, 1);
   mpz_clear(mrb, &r);
 }
 
@@ -655,7 +655,7 @@ mpz_mdivmod(mrb_state *mrb, mpz_t *q, mpz_t *r, mpz_t *x, mpz_t *y)
     q->sn = 0;
   /* now if r != 0 and q < 0 we need to round q towards -inf */
   if (!uzero_p(r) && qsign < 0)
-    mpz_sub_int(mrb, q, 1);
+    mpz_add_int(mrb, q, 1);
 }
 
 static void
@@ -908,7 +908,7 @@ mpz_get_str(mrb_state *mrb, char *s, mrb_int sz, mrb_int base, mpz_t *x)
       }
 
       // convert to character
-      for (mp_limb b=b2/base; b>0; b/=base) {
+      for (mp_limb b=b2; b>=base; b/=base) {
         char a0 = (char)(a % base);
         if (a0 < 10) a0 += '0';
         else a0 += 'a' - 10;
@@ -1134,8 +1134,7 @@ mpz_pow(mrb_state *mrb, mpz_t *zz, mpz_t *x, mrb_int e)
     return;
   }
 
-  mpz_init(mrb, &t);
-  mpz_set(mrb, &t, x);
+  mpz_init_set(mrb, &t, x);
   for (;!(mask &e); mask>>=1)
     ;
   mask>>=1;
@@ -1509,6 +1508,8 @@ mrb_bint_add_n(mrb_state *mrb, mrb_value x, mrb_value y)
       else {
         mpz_add_int(mrb, &z, n<0 ? -n : n);
       }
+      struct RBigint *v = bint_new(mrb, &z);
+      return mrb_obj_value(v);
     }
   }
   y = mrb_as_bint(mrb, y);
@@ -1912,15 +1913,15 @@ mrb_bint_xor(mrb_state *mrb, mrb_value x, mrb_value y)
   mpz_t a, b, c;
 
   bint_as_mpz(RBIGINT(x), &a);
-  if (mrb_integer_p(y)) {
+  if (mrb_integer_p(y) && a.sn > 0) {
     mrb_int z = mrb_integer(y);
     if (z == 0) return x;
     if (0 < z && (mp_dbl_limb)z < DIG_BASE) {
-      z ^= a.p[0];
-      return mrb_int_value(mrb, z);
+      mpz_init_set(mrb, &c, &a);
+      c.p[0] ^= z;
+      return bint_norm(mrb, bint_new(mrb, &c));
     }
   }
-
   y = mrb_as_bint(mrb, y);
   bint_as_mpz(RBIGINT(y), &b);
   if (zero_p(&a)) return y;
diff --git a/mrbgems/mruby-io/include/mruby/ext/io.h b/mrbgems/mruby-io/include/mruby/ext/io.h
index 61f7533f5..537bf09c8 100644
--- a/mrbgems/mruby-io/include/mruby/ext/io.h
+++ b/mrbgems/mruby-io/include/mruby/ext/io.h
@@ -6,7 +6,6 @@
 #define MRUBY_IO_H
 
 #include <mruby.h>
-#include <mruby/presym.h>
 
 #ifdef MRB_NO_STDIO
 # error IO and File conflicts 'MRB_NO_STDIO' in your build configuration
@@ -66,8 +65,8 @@ struct mrb_io {
 #define MRB_O_DSYNC             0x00008000
 #define MRB_O_RSYNC             0x00010000
 
-#define E_IO_ERROR              mrb_exc_get_id(mrb, MRB_SYM(IOError))
-#define E_EOF_ERROR             mrb_exc_get_id(mrb, MRB_SYM(EOFError))
+#define E_IO_ERROR              mrb_exc_get_id(mrb, MRB_ERROR_SYM(IOError))
+#define E_EOF_ERROR             mrb_exc_get_id(mrb, MRB_ERROR_SYM(EOFError))
 
 int mrb_io_fileno(mrb_state *mrb, mrb_value io);
 
diff --git a/mrbgems/mruby-io/mrblib/file.rb b/mrbgems/mruby-io/mrblib/file.rb
index 719f4e629..e5594ca50 100644
--- a/mrbgems/mruby-io/mrblib/file.rb
+++ b/mrbgems/mruby-io/mrblib/file.rb
@@ -149,7 +149,7 @@ class File < IO
     if drive_prefix.empty?
       expanded_path
     else
-      drive_prefix + expanded_path.gsub("/", File::ALT_SEPARATOR)
+      drive_prefix + expanded_path
     end
   end
 
diff --git a/mrbgems/mruby-io/src/file.c b/mrbgems/mruby-io/src/file.c
index 8ea3202ea..4759a401c 100644
--- a/mrbgems/mruby-io/src/file.c
+++ b/mrbgems/mruby-io/src/file.c
@@ -345,15 +345,14 @@ mrb_file__gethome(mrb_state *mrb, mrb_value klass)
   mrb_int argc = mrb_get_args(mrb, "|S", &username);
   if (argc == 0) {
     home = getenv("HOME");
-    if (home == NULL) {
-      return mrb_nil_value();
-    }
 #ifdef _WIN32
-    home = getenv("USERPROFILE");
     if (home == NULL) {
-      return mrb_nil_value();
+      home = getenv("USERPROFILE");
     }
 #endif
+    if (home == NULL) {
+      return mrb_nil_value();
+    }
     if (!mrb_file_is_absolute_path(home)) {
       mrb_raise(mrb, E_ARGUMENT_ERROR, "non-absolute home");
     }
@@ -378,6 +377,15 @@ mrb_file__gethome(mrb_state *mrb, mrb_value klass)
   home = mrb_utf8_from_locale(home, -1);
   path = mrb_str_new_cstr(mrb, home);
   mrb_utf8_free(home);
+#ifdef _WIN32
+  char *pathp = RSTRING_PTR(path);
+  const char *const pathend = pathp + RSTRING_LEN(path);
+  for (;;) {
+    pathp = memchr(pathp, '\\', pathend - pathp);
+    if (!pathp) break;
+    *pathp++ = '/';
+  }
+#endif
   return path;
 }
 
diff --git a/mrbgems/mruby-io/src/file_test.c b/mrbgems/mruby-io/src/file_test.c
index e04f970b2..342c29a70 100644
--- a/mrbgems/mruby-io/src/file_test.c
+++ b/mrbgems/mruby-io/src/file_test.c
@@ -8,6 +8,7 @@
 #include <mruby/string.h>
 #include <mruby/ext/io.h>
 #include <mruby/error.h>
+#include <mruby/presym.h>
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -38,7 +39,7 @@ extern struct mrb_data_type mrb_io_type;
 static int
 mrb_stat0(mrb_state *mrb, mrb_value obj, struct stat *st, int do_lstat)
 {
-  if (mrb_obj_is_kind_of(mrb, obj, mrb_class_get(mrb, "IO"))) {
+  if (mrb_obj_is_kind_of(mrb, obj, mrb_class_get_id(mrb, MRB_SYM(IO)))) {
     struct mrb_io *fptr;
     fptr = (struct mrb_io*)mrb_data_get_ptr(mrb, obj, &mrb_io_type);
 
@@ -337,16 +338,16 @@ mrb_init_file_test(mrb_state *mrb)
 {
   struct RClass *f;
 
-  f = mrb_define_class(mrb, "FileTest", mrb->object_class);
+  f = mrb_define_class_id(mrb, MRB_SYM(FileTest), mrb->object_class);
 
-  mrb_define_class_method(mrb, f, "directory?", mrb_filetest_s_directory_p, MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "exist?",     mrb_filetest_s_exist_p,     MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "exists?",    mrb_filetest_s_exist_p,     MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "file?",      mrb_filetest_s_file_p,      MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "pipe?",      mrb_filetest_s_pipe_p,      MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "size",       mrb_filetest_s_size,        MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "size?",      mrb_filetest_s_size_p,      MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "socket?",    mrb_filetest_s_socket_p,    MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "symlink?",   mrb_filetest_s_symlink_p,   MRB_ARGS_REQ(1));
-  mrb_define_class_method(mrb, f, "zero?",      mrb_filetest_s_zero_p,      MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(directory), mrb_filetest_s_directory_p, MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(exist),     mrb_filetest_s_exist_p,     MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(exists),    mrb_filetest_s_exist_p,     MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(file),      mrb_filetest_s_file_p,      MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(pipe),      mrb_filetest_s_pipe_p,      MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM(size),        mrb_filetest_s_size,        MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(size),      mrb_filetest_s_size_p,      MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(socket),    mrb_filetest_s_socket_p,    MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(symlink),   mrb_filetest_s_symlink_p,   MRB_ARGS_REQ(1));
+  mrb_define_class_method_id(mrb, f, MRB_SYM_Q(zero),      mrb_filetest_s_zero_p,      MRB_ARGS_REQ(1));
 }
diff --git a/mrbgems/mruby-io/test/file.rb b/mrbgems/mruby-io/test/file.rb
index 5746986ad..07e32b325 100644
--- a/mrbgems/mruby-io/test/file.rb
+++ b/mrbgems/mruby-io/test/file.rb
@@ -204,19 +204,19 @@ assert('File.expand_path') do
   assert_equal "/", File.expand_path("../../../..", "/")
   if File._getwd[1] == ":"
     drive_letter = File._getwd[0]
-    assert_equal drive_letter + ":\\", File.expand_path(([".."] * 100).join("/"))
+    assert_equal drive_letter + ":/", File.expand_path(([".."] * 100).join("/"))
   else
     assert_equal "/", File.expand_path(([".."] * 100).join("/"))
   end
 end
 
-assert('File.expand_path (with ENV)') do
-  skip unless Object.const_defined?(:ENV) && ENV['HOME']
+assert('File.expand_path (with getenv(3))') do
+  skip unless MRubyIOTestUtil.const_defined?(:ENV_HOME)
 
-  assert_equal ENV['HOME'], File.expand_path("~/"),      "home"
-  assert_equal ENV['HOME'], File.expand_path("~/", "/"), "home with base_dir"
+  assert_equal MRubyIOTestUtil::ENV_HOME, File.expand_path("~/"),      "home"
+  assert_equal MRubyIOTestUtil::ENV_HOME, File.expand_path("~/", "/"), "home with base_dir"
 
-  assert_equal "#{ENV['HOME']}/user", File.expand_path("user", ENV['HOME']), "relative with base_dir"
+  assert_equal "#{MRubyIOTestUtil::ENV_HOME}/user", File.expand_path("user", MRubyIOTestUtil::ENV_HOME), "relative with base_dir"
 end
 
 assert('File.path') do
diff --git a/mrbgems/mruby-io/test/mruby_io_test.c b/mrbgems/mruby-io/test/mruby_io_test.c
index a00a911cf..18989a20c 100644
--- a/mrbgems/mruby-io/test/mruby_io_test.c
+++ b/mrbgems/mruby-io/test/mruby_io_test.c
@@ -243,4 +243,26 @@ mrb_mruby_io_gem_test(mrb_state* mrb)
   mrb_define_class_method(mrb, io_test, "win?", mrb_io_win_p, MRB_ARGS_NONE());
 
   mrb_define_const(mrb, io_test, "MRB_WITH_IO_PREAD_PWRITE", mrb_bool_value(MRB_WITH_IO_PREAD_PWRITE_ENABLED));
+
+  const char *env_home = getenv("HOME");
+#ifdef _WIN32
+  if (!env_home) {
+    env_home = getenv("USERPROFILE");
+  }
+#endif
+  if (env_home) {
+    char *utf8 = mrb_utf8_from_locale(env_home, strlen(env_home));
+    mrb_value path = mrb_str_new_cstr(mrb, utf8);
+#ifdef _WIN32
+    char *pathp = RSTRING_PTR(path);
+    const char *const pathend = pathp + RSTRING_LEN(path);
+    for (;;) {
+      pathp = memchr(pathp, '\\', pathend - pathp);
+      if (!pathp) break;
+      *pathp++ = '/';
+    }
+#endif
+    mrb_define_const(mrb, io_test, "ENV_HOME", path);
+    mrb_utf8_free(utf8);
+  }
 }
diff --git a/src/numeric.c b/src/numeric.c
index bfa8465f3..9fe516b10 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -1111,6 +1111,9 @@ int_mod(mrb_state *mrb, mrb_value x)
   if (mrb_bigint_p(x)) {
     return mrb_bint_mod(mrb, x, y);
   }
+  if (mrb_bigint_p(y)) {
+    return mrb_bint_mod(mrb, mrb_as_bint(mrb, x), y);
+  }
 #endif
   a = mrb_integer(x);
   if (a == 0) return x;
@@ -1159,6 +1162,9 @@ int_divmod(mrb_state *mrb, mrb_value x)
 #endif
     return mrb_bint_divmod(mrb, x, y);
   }
+  if (mrb_bigint_p(y)) {
+    return mrb_bint_divmod(mrb, mrb_as_bint(mrb, x), y);
+  }
 #endif
   if (mrb_integer_p(y)) {
     mrb_int div, mod;