diff --git a/sphinx/util/osutil.py b/sphinx/util/osutil.py
index 5becc37df..131c6b9c7 100644
--- a/sphinx/util/osutil.py
+++ b/sphinx/util/osutil.py
@@ -40,12 +40,20 @@ def relative_uri(base, to):
         return to
     b2 = base.split(SEP)
     t2 = to.split(SEP)
-    # remove common segments
-    for x, y in zip(b2, t2):
+    # remove common segments (except the last segment)
+    for x, y in zip(b2[:-1], t2[:-1]):
         if x != y:
             break
         b2.pop(0)
         t2.pop(0)
+    if b2 == t2:
+        # Special case: relative_uri('f/index.html','f/index.html')
+        # returns '', not 'index.html'
+        return ''
+    if len(b2) == 1 and t2 == ['']:
+        # Special case: relative_uri('f/index.html','f/') should 
+        # return './', not ''
+        return '.' +  SEP
     return ('..' + SEP) * (len(b2)-1) + SEP.join(t2)