diff --git a/mercurial/pure/parsers.py b/mercurial/pure/parsers.py
--- a/mercurial/pure/parsers.py
+++ b/mercurial/pure/parsers.py
@@ -243,21 +243,8 @@ def parse_index2(data, inline, revlogv2=
 
 
 class Index2Mixin(object):
-    #  6 bytes: offset
-    #  2 bytes: flags
-    #  4 bytes: compressed length
-    #  4 bytes: uncompressed length
-    #  4 bytes: base rev
-    #  4 bytes: link rev
-    #  4 bytes: parent 1 rev
-    #  4 bytes: parent 2 rev
-    # 32 bytes: nodeid
-    #  8 bytes: sidedata offset
-    #  4 bytes: sidedata compressed length
-    #  20 bytes: Padding to align to 96 bytes (see RevlogV2Plan wiki page)
-    index_format = b">Qiiiiii20s12xQi20x"
-    index_size = struct.calcsize(index_format)
-    assert index_size == 96, index_size
+    index_format = revlog_constants.INDEX_ENTRY_V2.format
+    index_size = revlog_constants.INDEX_ENTRY_V2.size
     null_item = (0, 0, 0, -1, -1, -1, -1, nullid, 0, 0)
 
     def replace_sidedata_info(self, i, sidedata_offset, sidedata_length):
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -43,6 +43,7 @@ from .revlogutils.constants import (
     FLAG_INLINE_DATA,
     INDEX_ENTRY_V0,
     INDEX_ENTRY_V1,
+    INDEX_ENTRY_V2,
     REVLOGV0,
     REVLOGV1,
     REVLOGV1_FLAGS,
@@ -87,7 +88,6 @@ from .utils import (
     storageutil,
     stringutil,
 )
-from .pure import parsers as pureparsers
 
 # blanked usage of all the name to prevent pyflakes constraints
 # We need these name available in the module for extensions.
@@ -352,20 +352,16 @@ class revlogio(object):
         return p
 
 
-indexformatv2 = struct.Struct(pureparsers.Index2Mixin.index_format)
-indexformatv2_pack = indexformatv2.pack
-
-
 class revlogv2io(object):
     def __init__(self):
-        self.size = indexformatv2.size
+        self.size = INDEX_ENTRY_V2.size
 
     def parseindex(self, data, inline):
         index, cache = parsers.parse_index2(data, inline, revlogv2=True)
         return index, cache
 
     def packentry(self, entry, node, version, rev):
-        p = indexformatv2_pack(*entry)
+        p = INDEX_ENTRY_V2.pack(*entry)
         if rev == 0:
             p = versionformat_pack(version) + p[4:]
         return p
diff --git a/mercurial/revlogutils/constants.py b/mercurial/revlogutils/constants.py
--- a/mercurial/revlogutils/constants.py
+++ b/mercurial/revlogutils/constants.py
@@ -57,6 +57,21 @@ INDEX_ENTRY_V0 = struct.Struct(b">4l20s2
 INDEX_ENTRY_V1 = struct.Struct(b">Qiiiiii20s12x")
 assert INDEX_ENTRY_V1.size == 32 * 2
 
+#  6 bytes: offset
+#  2 bytes: flags
+#  4 bytes: compressed length
+#  4 bytes: uncompressed length
+#  4 bytes: base rev
+#  4 bytes: link rev
+#  4 bytes: parent 1 rev
+#  4 bytes: parent 2 rev
+# 32 bytes: nodeid
+#  8 bytes: sidedata offset
+#  4 bytes: sidedata compressed length
+#  20 bytes: Padding to align to 96 bytes (see RevlogV2Plan wiki page)
+INDEX_ENTRY_V2 = struct.Struct(b">Qiiiiii20s12xQi20x")
+assert INDEX_ENTRY_V2.size == 32 * 3
+
 # revlog index flags
 
 # For historical reasons, revlog's internal flags were exposed via the