diff --git a/mercurial/bundlerepo.py b/mercurial/bundlerepo.py
--- a/mercurial/bundlerepo.py
+++ b/mercurial/bundlerepo.py
@@ -80,7 +80,7 @@
             # start, size, full unc. size, base (unused), link, p1, p2, node
             e = (revlog.offset_type(start, flags), size, -1, baserev, link,
                  self.rev(p1), self.rev(p2), node)
-            self.index.insert(-1, e)
+            self.index.append(e)
             self.nodemap[node] = n
             self.bundlerevs.add(n)
             n += 1
diff --git a/mercurial/cext/revlog.c b/mercurial/cext/revlog.c
--- a/mercurial/cext/revlog.c
+++ b/mercurial/cext/revlog.c
@@ -272,16 +272,12 @@
 	return -1;
 }
 
-static PyObject *index_insert(indexObject *self, PyObject *args)
+
+static PyObject *index_append(indexObject *self, PyObject *obj)
 {
-	PyObject *obj;
 	char *node;
-	int index;
 	Py_ssize_t len;
 
-	if (!PyArg_ParseTuple(args, "iO", &index, &obj))
-		return NULL;
-
 	if (!PyTuple_Check(obj) || PyTuple_GET_SIZE(obj) != 8) {
 		PyErr_SetString(PyExc_TypeError, "8-tuple required");
 		return NULL;
@@ -292,15 +288,6 @@
 
 	len = index_length(self);
 
-	if (index < 0)
-		index += len;
-
-	if (index != len - 1) {
-		PyErr_SetString(PyExc_IndexError,
-				"insert only supported at index -1");
-		return NULL;
-	}
-
 	if (self->added == NULL) {
 		self->added = PyList_New(0);
 		if (self->added == NULL)
@@ -311,7 +298,7 @@
 		return NULL;
 
 	if (self->nt)
-		nt_insert(self, node, index);
+		nt_insert(self, node, len - 1);
 
 	Py_CLEAR(self->headrevs);
 	Py_RETURN_NONE;
@@ -2065,8 +2052,8 @@
 	 "get filtered head revisions"}, /* Can always do filtering */
 	{"deltachain", (PyCFunction)index_deltachain, METH_VARARGS,
 	 "determine revisions with deltas to reconstruct fulltext"},
-	{"insert", (PyCFunction)index_insert, METH_VARARGS,
-	 "insert an index entry"},
+	{"append", (PyCFunction)index_append, METH_O,
+	 "append an index entry"},
 	{"partialmatch", (PyCFunction)index_partialmatch, METH_VARARGS,
 	 "match a potentially ambiguous node ID"},
 	{"shortest", (PyCFunction)index_shortest, METH_VARARGS,
diff --git a/mercurial/pure/parsers.py b/mercurial/pure/parsers.py
--- a/mercurial/pure/parsers.py
+++ b/mercurial/pure/parsers.py
@@ -41,8 +41,7 @@
     def __len__(self):
         return self._lgt + len(self._extra) + 1
 
-    def insert(self, i, tup):
-        assert i == -1
+    def append(self, tup):
         self._extra.append(tup)
 
     def _fix_index(self, i):
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -2549,7 +2549,7 @@
 
         e = (offset_type(offset, flags), l, textlen,
              base, link, p1r, p2r, node)
-        self.index.insert(-1, e)
+        self.index.append(e)
         self.nodemap[node] = curr
 
         entry = self._io.packentry(e, self.node, self.version, curr)
diff --git a/mercurial/unionrepo.py b/mercurial/unionrepo.py
--- a/mercurial/unionrepo.py
+++ b/mercurial/unionrepo.py
@@ -73,7 +73,7 @@
             # I have no idea if csize is valid in the base revlog context.
             e = (flags, None, rsize, base,
                  link, self.rev(p1node), self.rev(p2node), node)
-            self.index.insert(-1, e)
+            self.index.append(e)
             self.nodemap[node] = n
             self.bundlerevs.add(n)
             n += 1