diff --git a/hgext/patchbomb.py b/hgext/patchbomb.py
--- a/hgext/patchbomb.py
+++ b/hgext/patchbomb.py
@@ -159,7 +159,7 @@ def makepatch(ui, repo, patch, opts, _ch
                 patchname = patchtags[0]
             elif total > 1:
                 patchname = cmdutil.make_filename(repo, '%b-%n.patch',
-                                                  binnode, idx, total)
+                                                  binnode, seqno=idx, total=total)
             else:
                 patchname = cmdutil.make_filename(repo, '%b.patch', binnode)
         disposition = 'inline'
diff --git a/tests/test-patchbomb.out b/tests/test-patchbomb.out
--- a/tests/test-patchbomb.out
+++ b/tests/test-patchbomb.out
@@ -386,7 +386,7 @@ Cc: bar
 Content-Type: text/x-patch; charset="us-ascii"
 MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
-Content-Disposition: inline; filename=t2-2.patch
+Content-Disposition: inline; filename=t2-1.patch
 
 # HG changeset patch
 # User test
@@ -522,7 +522,7 @@ Patch subject is complete summary.
 Content-Type: text/x-patch; charset="us-ascii"
 MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
-Content-Disposition: attachment; filename=t2-2.patch
+Content-Disposition: attachment; filename=t2-1.patch
 
 # HG changeset patch
 # User test
@@ -650,7 +650,7 @@ Cc: bar
 Content-Type: text/x-patch; charset="us-ascii"
 MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
-Content-Disposition: inline; filename=t2-2.patch
+Content-Disposition: inline; filename=t2-1.patch
 
 # HG changeset patch
 # User test