diff --git a/CHANGES b/CHANGES
index c82c5b710..88d91b7a1 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,11 @@
 Release 0.5.2 (in development)
 ==============================
 
+* #81: Write environment and search index in a manner that is safe
+  from exceptions that occur during dumping.
+
+* #80: Fix UnicodeErrors when a locale is set with setlocale().
+
 
 Release 0.5.1 (Dec 15, 2008)
 ============================
diff --git a/sphinx/builder.py b/sphinx/builder.py
index 81fc24862..3f3ec2c9e 100644
--- a/sphinx/builder.py
+++ b/sphinx/builder.py
@@ -5,7 +5,7 @@
 
     Builder classes for different output formats.
 
-    :copyright: 2007-2008 by Georg Brandl, Sebastian Wiesner, Horst Gutmann.
+    :copyright: 2007-2009 by Georg Brandl, Sebastian Wiesner, Horst Gutmann.
     :license: BSD.
 """
 
@@ -775,11 +775,15 @@ class StandaloneHTMLBuilder(Builder):
     def handle_finish(self):
         self.info(bold('dumping search index... '), nonl=True)
         self.indexer.prune(self.env.all_docs)
-        f = open(path.join(self.outdir, self.searchindex_filename), 'wb')
+        searchindexfn = path.join(self.outdir, self.searchindex_filename)
+        # first write to a temporary file, so that if dumping fails, the existing
+        # index won't be overwritten
+        f = open(searchindexfn + '.tmp', 'wb')
         try:
             self.indexer.dump(f, self.indexer_format)
         finally:
             f.close()
+        os.rename(searchindexfn + '.tmp', searchindexfn)
         self.info('done')
 
         self.info(bold('dumping object inventory... '), nonl=True)
diff --git a/sphinx/environment.py b/sphinx/environment.py
index 795e4594d..62ae4b03b 100644
--- a/sphinx/environment.py
+++ b/sphinx/environment.py
@@ -5,7 +5,7 @@
 
     Global creation environment.
 
-    :copyright: 2007-2008 by Georg Brandl.
+    :copyright: 2007-2009 by Georg Brandl.
     :license: BSD.
 """
 
@@ -203,7 +203,9 @@ class BuildEnvironment:
         self.set_warnfunc(None)
         values = self.config.values
         del self.config.values
-        picklefile = open(filename, 'wb')
+        # first write to a temporary file, so that if dumping fails, the existing
+        # environment won't be overwritten
+        picklefile = open(filename + '.tmp', 'wb')
         # remove potentially pickling-problematic values from config
         for key, val in vars(self.config).items():
             if key.startswith('_') or \
@@ -215,6 +217,7 @@ class BuildEnvironment:
             pickle.dump(self, picklefile, pickle.HIGHEST_PROTOCOL)
         finally:
             picklefile.close()
+        os.rename(filename + '.tmp', filename)
         # reset attributes
         self.config.values = values
         self.set_warnfunc(warnfunc)