diff --git a/ChangeLog b/ChangeLog
index 37e4b9007b..65704ecd43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Aug 19 23:55:29 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* process.c (rb_f_spawn): [DOC] elaborate environment variable
+	  values.  [ruby-core:70456] [Bug #11463]
+
 Wed Aug 19 23:48:06 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* win32/win32.c (winnt_lstat): check reparse point tags and treat
diff --git a/process.c b/process.c
index 206a44546c..2366cbd289 100644
--- a/process.c
+++ b/process.c
@@ -4017,7 +4017,7 @@ rb_f_system(int argc, VALUE *argv)
  *      name => val : set the environment variable
  *      name => nil : unset the environment variable
  *
- *      the keys must be strings.
+ *      the keys and the values except for +nil+ must be strings.
  *    command...:
  *      commandline                 : command line string which is passed to the standard shell
  *      cmdname, arg1, ...          : command name and one or more arguments (This form does not use the shell. See below for caveats.)