diff --git a/src/allmydata/immutable/upload.py b/src/allmydata/immutable/upload.py
index 5149ba9db..41b338e33 100644
--- a/src/allmydata/immutable/upload.py
+++ b/src/allmydata/immutable/upload.py
@@ -48,8 +48,8 @@ class UploadResults(Copyable, RemoteCopy):
 
     def __init__(self):
         self.timings = {} # dict of name to number of seconds
-        self.sharemap = {} # dict of shnum to placement string
-        self.servermap = {} # dict of peerid to set(shnums)
+        self.sharemap = {} # k: shnum, v: set(serverid)
+        self.servermap = {} # k: serverid, v: set(shnum)
         self.file_size = None
         self.ciphertext_fetched = None # how much the helper fetched
         self.uri = None
@@ -654,6 +654,9 @@ class CHKUploader:
         self._upload_status.set_active(True)
         self._upload_status.set_results(self._results)
 
+        # locate_all_shareholders() will create the following attribute:
+        # self._peer_trackers = {} # k: shnum, v: instance of PeerTracker
+
     def log(self, *args, **kwargs):
         if "parent" not in kwargs:
             kwargs["parent"] = self._log_number
@@ -735,22 +738,16 @@ class CHKUploader:
         """
         self.log("_send_shares, used_peers is %s" % (used_peers,))
         # record already-present shares in self._results
-        for (shnum, peerid) in already_peers.items():
-            peerid_s = idlib.shortnodeid_b2a(peerid)
-            self._results.sharemap[shnum] = "Found on [%s]" % peerid_s
-            if peerid not in self._results.servermap:
-                self._results.servermap[peerid] = set()
-            self._results.servermap[peerid].add(shnum)
         self._results.preexisting_shares = len(already_peers)
 
-        self._sharemap = {}
+        self._peer_trackers = {} # k: shnum, v: instance of PeerTracker
         for peer in used_peers:
             assert isinstance(peer, PeerTracker)
         buckets = {}
         for peer in used_peers:
             buckets.update(peer.buckets)
             for shnum in peer.buckets:
-                self._sharemap[shnum] = peer
+                self._peer_trackers[shnum] = peer
         assert len(buckets) == sum([len(peer.buckets) for peer in used_peers])
         encoder.set_shareholders(buckets)
 
@@ -758,13 +755,11 @@ class CHKUploader:
         """ Returns a Deferred that will fire with the UploadResults instance. """
         r = self._results
         for shnum in self._encoder.get_shares_placed():
-            peer_tracker = self._sharemap[shnum]
+            peer_tracker = self._peer_trackers[shnum]
             peerid = peer_tracker.peerid
             peerid_s = idlib.shortnodeid_b2a(peerid)
-            r.sharemap[shnum] = "Placed on [%s]" % peerid_s
-            if peerid not in r.servermap:
-                r.servermap[peerid] = set()
-            r.servermap[peerid].add(shnum)
+            r.sharemap.setdefault(shnum, set()).add(peerid)
+            r.servermap.setdefault(peerid, set()).add(shnum)
         r.pushed_shares = len(self._encoder.get_shares_placed())
         now = time.time()
         r.file_size = self._encoder.file_size
diff --git a/src/allmydata/interfaces.py b/src/allmydata/interfaces.py
index 129727427..54176c692 100644
--- a/src/allmydata/interfaces.py
+++ b/src/allmydata/interfaces.py
@@ -1460,7 +1460,13 @@ class IUploadResults(Interface):
      .file_size : the size of the file, in bytes
      .uri : the CHK read-cap for the file
      .ciphertext_fetched : how many bytes were fetched by the helper
-     .sharemap : dict mapping share number to placement string
+     .renamed_sharemap: dict mapping share identifier to set of serverids
+                   (binary strings). This indicates which servers were given
+                   which shares. For immutable files, the shareid is an
+                   integer (the share number, from 0 to N-1). For mutable
+                   files, it is a string of the form 'seq%d-%s-sh%d',
+                   containing the sequence number, the roothash, and the
+                   share number.
      .servermap : dict mapping server peerid to a set of share numbers
      .timings : dict of timing information, mapping name to seconds (float)
        total : total upload time, start to finish
diff --git a/src/allmydata/web/status.py b/src/allmydata/web/status.py
index f97ca515d..9f508813d 100644
--- a/src/allmydata/web/status.py
+++ b/src/allmydata/web/status.py
@@ -46,8 +46,10 @@ class UploadResultsRendererMixin(RateAndTimeMixin):
             if sharemap is None:
                 return "None"
             l = T.ul()
-            for shnum in sorted(sharemap.keys()):
-                l[T.li["%d -> %s" % (shnum, sharemap[shnum])]]
+            for shnum, peerids in sorted(sharemap.items()):
+                for peerid in peerids:
+                    peerid_s = idlib.shortnodeid_b2a(peerid)
+                    l[T.li["%d -> %s" % (shnum, peerid_s)]]
             return l
         d.addCallback(_render)
         return d