diff --git a/doc/manual/conf-file.xml b/doc/manual/conf-file.xml
index 176035248..79faa05fd 100644
--- a/doc/manual/conf-file.xml
+++ b/doc/manual/conf-file.xml
@@ -118,6 +118,26 @@ env-keep-derivations = false
   </varlistentry>
 
 
+  <varlistentry><term><literal>system</literal></term>
+
+    <listitem><para>This option specifies the canonical Nix system
+    name of the current installation, such as
+    <literal>i686-linux</literal> or
+    <literal>powerpc-darwin</literal>.  Nix can only build derivations
+    whose <literal>system</literal> attribute equals the value
+    specified here.  In general, it never makes sense to modify this
+    value from its default, since you can use it to ‘lie’ about the
+    platform you are building on (e.g., perform a Mac OS build on a
+    Linux machine; the result would obviously be wrong).  It only
+    makes sense if the Nix binaries can run on multiple platforms,
+    e.g., ‘universal binaries’ that run on <literal>powerpc-darwin</literal> and
+    <literal>i686-darwin</literal>.</para>
+
+    <para>It defaults to the canonical Nix system name detected by
+    <filename>configure</filename> at build time.</para></listitem>
+
+  </varlistentry>
+  
     
 </variablelist>
 
diff --git a/doc/manual/opt-common.xml b/doc/manual/opt-common.xml
index fcfeca858..04cda1531 100644
--- a/doc/manual/opt-common.xml
+++ b/doc/manual/opt-common.xml
@@ -93,8 +93,12 @@
   <term><option>-j</option></term>
 
   <listitem><para>Sets the maximum number of build jobs that Nix will
-  perform in parallel to the specified number.  The default is 1.  A
-  higher value is useful on SMP systems or to exploit I/O latency.</para></listitem>
+  perform in parallel to the specified number.  The default is
+  specified by the <link
+  linkend='conf-build-max-jobs'><literal>build-max-jobs</literal></link>
+  configuration setting, which itself defaults to
+  <literal>1</literal>.  A higher value is useful on SMP systems or to
+  exploit I/O latency.  </para></listitem>
   
 </varlistentry>