diff --git a/mercurial/changegroup.py b/mercurial/changegroup.py
--- a/mercurial/changegroup.py
+++ b/mercurial/changegroup.py
@@ -658,15 +658,15 @@
 
 def deltagroup(repo, store, nodes, ischangelog, lookup, forcedeltaparentprev,
                allowreorder,
-               units=None,
+               topic=None,
                ellipses=False, clrevtolocalrev=None, fullclnodes=None,
                precomputedellipsis=None):
     """Calculate deltas for a set of revisions.
 
     Is a generator of ``revisiondelta`` instances.
 
-    If units is not None, progress detail will be generated, units specifies
-    the type of revlog that is touched (changelog, manifest, etc.).
+    If topic is not None, progress detail will be generated using this
+    topic name (e.g. changesets, manifests, etc).
     """
     if not nodes:
         return
@@ -743,8 +743,8 @@
     # We expect the first pass to be fast, so we only engage the progress
     # meter for constructing the revision deltas.
     progress = None
-    if units is not None:
-        progress = repo.ui.makeprogress(_('bundling'), unit=units,
+    if topic is not None:
+        progress = repo.ui.makeprogress(topic, unit=_('chunks'),
                                         total=len(requests))
 
     for i, delta in enumerate(store.emitrevisiondeltas(requests)):
@@ -1002,7 +1002,7 @@
             # Reorder settings are currently ignored for changelog.
             True,
             ellipses=self._ellipses,
-            units=_('changesets'),
+            topic=_('changesets'),
             clrevtolocalrev={},
             fullclnodes=self._fullclnodes,
             precomputedellipsis=self._precomputedellipsis)
@@ -1083,7 +1083,7 @@
                 self._repo, store, prunednodes, False, lookupfn,
                 self._forcedeltaparentprev, self._reorder,
                 ellipses=self._ellipses,
-                units=_('manifests'),
+                topic=_('manifests'),
                 clrevtolocalrev=clrevtolocalrev,
                 fullclnodes=self._fullclnodes,
                 precomputedellipsis=self._precomputedellipsis)
@@ -1140,7 +1140,7 @@
             linknodes = normallinknodes
 
         repo = self._repo
-        progress = repo.ui.makeprogress(_('bundling'), unit=_('files'),
+        progress = repo.ui.makeprogress(_('files'), unit=_('files'),
                                         total=len(changedfiles))
         for i, fname in enumerate(sorted(changedfiles)):
             filerevlog = repo.file(fname)
diff --git a/tests/test-bundle.t b/tests/test-bundle.t
--- a/tests/test-bundle.t
+++ b/tests/test-bundle.t
@@ -796,13 +796,13 @@
   057f4db07f61970e1c11e83be79e9d08adc4dc31
   bundle2-output-bundle: "HG20", (1 params) 2 parts total
   bundle2-output-part: "changegroup" (params: 1 mandatory 1 advisory) streamed payload
-  bundling: 1/2 changesets (50.00%)
-  bundling: 2/2 changesets (100.00%)
-  bundling: 1/2 manifests (50.00%)
-  bundling: 2/2 manifests (100.00%)
-  bundling: b 1/3 files (33.33%)
-  bundling: b1 2/3 files (66.67%)
-  bundling: x 3/3 files (100.00%)
+  changesets: 1/2 chunks (50.00%)
+  changesets: 2/2 chunks (100.00%)
+  manifests: 1/2 chunks (50.00%)
+  manifests: 2/2 chunks (100.00%)
+  files: b 1/3 files (33.33%)
+  files: b1 2/3 files (66.67%)
+  files: x 3/3 files (100.00%)
   bundle2-output-part: "cache:rev-branch-cache" (advisory) streamed payload
 
 #if repobundlerepo
diff --git a/tests/test-bundle2-format.t b/tests/test-bundle2-format.t
--- a/tests/test-bundle2-format.t
+++ b/tests/test-bundle2-format.t
@@ -873,17 +873,17 @@
   bundle2-output-part: "changegroup" (advisory) streamed payload
   bundle2-output: part 0: "changegroup"
   bundle2-output: header chunk size: 18
-  bundling: 1/4 changesets (25.00%)
-  bundling: 2/4 changesets (50.00%)
-  bundling: 3/4 changesets (75.00%)
-  bundling: 4/4 changesets (100.00%)
-  bundling: 1/4 manifests (25.00%)
-  bundling: 2/4 manifests (50.00%)
-  bundling: 3/4 manifests (75.00%)
-  bundling: 4/4 manifests (100.00%)
-  bundling: D 1/3 files (33.33%)
-  bundling: E 2/3 files (66.67%)
-  bundling: H 3/3 files (100.00%)
+  changesets: 1/4 chunks (25.00%)
+  changesets: 2/4 chunks (50.00%)
+  changesets: 3/4 chunks (75.00%)
+  changesets: 4/4 chunks (100.00%)
+  manifests: 1/4 chunks (25.00%)
+  manifests: 2/4 chunks (50.00%)
+  manifests: 3/4 chunks (75.00%)
+  manifests: 4/4 chunks (100.00%)
+  files: D 1/3 files (33.33%)
+  files: E 2/3 files (66.67%)
+  files: H 3/3 files (100.00%)
   bundle2-output: payload chunk size: 1555
   bundle2-output: closing payload chunk
   bundle2-output: end of bundle