diff --git a/ChangeLog b/ChangeLog
index f0212a6e3a..fefbea8b9d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Sep  7 17:50:38 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* include/ruby/util.h (setenv): remove POSIX-noncompliant
+	  definition with 2 arguments.
+
 Wed Sep  7 17:35:37 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* unicode/8.0.0/casefold.h, name2ctype.h, unicode/data/8.0.0:
diff --git a/hash.c b/hash.c
index 0d963976b9..8d39c347c8 100644
--- a/hash.c
+++ b/hash.c
@@ -3350,8 +3350,6 @@ ruby_setenv(const char *name, const char *value)
 	invalid_envname(name);
     }
 #elif defined(HAVE_SETENV) && defined(HAVE_UNSETENV)
-#undef setenv
-#undef unsetenv
     if (value) {
 	if (setenv(name, value, 1))
 	    rb_sys_fail_str(rb_sprintf("setenv(%s)", name));
diff --git a/include/ruby/util.h b/include/ruby/util.h
index e9343b3390..3b78e467b4 100644
--- a/include/ruby/util.h
+++ b/include/ruby/util.h
@@ -64,10 +64,6 @@ void ruby_qsort(void *, const size_t, const size_t,
 
 void ruby_setenv(const char *, const char *);
 void ruby_unsetenv(const char *);
-#undef setenv
-#undef unsetenv
-#define setenv(name,val) ruby_setenv((name),(val))
-#define unsetenv(name,val) ruby_unsetenv(name)
 
 char *ruby_strdup(const char *);
 #undef strdup