diff --git a/doc/en/installation/source.rst b/doc/en/installation/source.rst
--- a/doc/en/installation/source.rst
+++ b/doc/en/installation/source.rst
@@ -636,21 +636,23 @@ process:
   spkg in a subdirectory of :file:`$SAGE_ROOT/spkg/build/`; for
   example, build :file:`atlas-3.8.3.p12.spkg` in the directory
   :file:`$SAGE_ROOT/spkg/build/atlas-3.8.3.p12/`.  If this variable is
-  set to an existing directory, build in
-  :file:`$SAGE_BUILD_TMPDIR/build/atlas-3.8.3.p12/` instead.  As of
-  this writing (Sage 4.7.1), when building the standard Sage packages,
-  this may require 1.5 gigabytes of free space in this directory
-  (or more if :envvar:`SAGE_KEEP_BUILT_SPKGS` is "yes" -- see below);
-  the exact amount of required space varies from platform to
-  platform.  For example, the block size of the file system will
-  affect the amount of space used, since some spkgs contain many small
-  files.
+  set, build in :file:`$SAGE_BUILD_TMPDIR/build/atlas-3.8.3.p12/`
+  instead.  If the directory :file:`$SAGE_BUILD_TMPDIR` does not
+  exist, it is created.  As of this writing (Sage 4.8), when building
+  the standard Sage packages, this may require 1.5 gigabytes of free
+  space in this directory (or more if :envvar:`SAGE_KEEP_BUILT_SPKGS`
+  is "yes" -- see below); the exact amount of required space varies
+  from platform to platform.  For example, the block size of the file
+  system will affect the amount of space used, since some spkgs
+  contain many small files.
 
   .. warning::
 
     The variable :envvar:`SAGE_BUILD_TMPDIR` must be set to the full
-    path name of an existing directory for which the user has write
-    permissions, and its path name must contain no spaces.
+    path name of either an existing directory for which the user has write
+    permissions, or to the full path name of a nonexistent directory
+    which the user has permission to create.  The path name must
+    contain no spaces.
 
 - :envvar:`SAGE_KEEP_BUILT_SPKGS` - the default behavior is to delete
   each build directory -- the appropriate subdirectory of
@@ -668,7 +670,7 @@ process:
 
   .. note::
 
-     After a full build of Sage (as of version 4.7.1), these
+     After a full build of Sage (as of version 4.8), these
      subdirectories can take up to 6 gigabytes of storage, in total,
      depending on the platform and the block size of the file system.
      If you always set this variable to "yes", it can take even more
@@ -1001,4 +1003,4 @@ Special Notes
   :ref:`installation in a multiuser environment
   <sagetex_installation_multiuser>`.
 
-  **This page was last updated in November 2011**
+  **This page was last updated in February 2012**