diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -342,7 +342,7 @@
             if len(labels) < 3:
                 labels.append('base')
         r = simplemerge.simplemerge(ui, fcd, fca, fco,
-                                    quiet=True, label=labels, repo=repo)
+                                    quiet=True, label=labels)
         if not r:
             ui.debug(" premerge successful\n")
             return 0
@@ -372,7 +372,7 @@
     ui = repo.ui
 
     r = simplemerge.simplemerge(ui, fcd, fca, fco,
-                                label=labels, mode=mode, repo=repo)
+                                label=labels, mode=mode)
     return True, r, False
 
 @internaltool('union', fullmerge,
@@ -424,8 +424,7 @@
     assert localorother is not None
     tool, toolpath, binary, symlink = toolconf
     r = simplemerge.simplemerge(repo.ui, fcd, fca, fco,
-                                label=labels, localorother=localorother,
-                                repo=repo)
+                                label=labels, localorother=localorother)
     return True, r
 
 @internaltool('merge-local', mergeonly, precheck=_mergecheck)
diff --git a/mercurial/simplemerge.py b/mercurial/simplemerge.py
--- a/mercurial/simplemerge.py
+++ b/mercurial/simplemerge.py
@@ -413,7 +413,7 @@
         result[i] = override
     return result
 
-def simplemerge(ui, localctx, basectx, otherctx, repo=None, **opts):
+def simplemerge(ui, localctx, basectx, otherctx, **opts):
     """Performs the simplemerge algorithm.
 
     The merged result is written into `localctx`.