diff --git a/mercurial/revlogutils/debug.py b/mercurial/revlogutils/debug.py
--- a/mercurial/revlogutils/debug.py
+++ b/mercurial/revlogutils/debug.py
@@ -80,6 +80,11 @@ def _nodeid(index, rev, entry, hexfn):
     return hexfn(entry[constants.ENTRY_NODE_ID])
 
 
+@debug_column(b"p1-rev", size=6, verbose=True)
+def _p1_rev(index, rev, entry, hexfn):
+    return b"%d" % entry[constants.ENTRY_PARENT_1]
+
+
 @debug_column(b"p1-nodeid", size=NODE_SIZE)
 def _p1_node(index, rev, entry, hexfn):
     parent = entry[constants.ENTRY_PARENT_1]
diff --git a/tests/test-debugcommands.t b/tests/test-debugcommands.t
--- a/tests/test-debugcommands.t
+++ b/tests/test-debugcommands.t
@@ -153,26 +153,26 @@ Test debugindex, with and without the --
        1       1 8cccb4b5fec2 07f494440405 000000000000
        2       2 b1e228c512c5 8cccb4b5fec2 000000000000
   $ hg debugindex -c --debug
-     rev linkrev                                   nodeid                                p1-nodeid                                p2-nodeid
-       0       0 07f4944404050f47db2e5c5071e0e84e7a27bba9 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
-       1       1 8cccb4b5fec20cafeb99dd01c26d4dee8ea4388a 07f4944404050f47db2e5c5071e0e84e7a27bba9 0000000000000000000000000000000000000000
-       2       2 b1e228c512c5d7066d70562ed839c3323a62d6d2 8cccb4b5fec20cafeb99dd01c26d4dee8ea4388a 0000000000000000000000000000000000000000
+     rev linkrev                                   nodeid p1-rev                                p1-nodeid                                p2-nodeid
+       0       0 07f4944404050f47db2e5c5071e0e84e7a27bba9     -1 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
+       1       1 8cccb4b5fec20cafeb99dd01c26d4dee8ea4388a      0 07f4944404050f47db2e5c5071e0e84e7a27bba9 0000000000000000000000000000000000000000
+       2       2 b1e228c512c5d7066d70562ed839c3323a62d6d2      1 8cccb4b5fec20cafeb99dd01c26d4dee8ea4388a 0000000000000000000000000000000000000000
   $ hg debugindex -m
      rev linkrev       nodeid    p1-nodeid    p2-nodeid
        0       0 a0c8bcbbb45c 000000000000 000000000000
        1       1 57faf8a737ae a0c8bcbbb45c 000000000000
        2       2 a35b10320954 57faf8a737ae 000000000000
   $ hg debugindex -m --debug
-     rev linkrev                                   nodeid                                p1-nodeid                                p2-nodeid
-       0       0 a0c8bcbbb45c63b90b70ad007bf38961f64f2af0 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
-       1       1 57faf8a737ae7faf490582941a82319ba6529dca a0c8bcbbb45c63b90b70ad007bf38961f64f2af0 0000000000000000000000000000000000000000
-       2       2 a35b103209548032201c16c7688cb2657f037a38 57faf8a737ae7faf490582941a82319ba6529dca 0000000000000000000000000000000000000000
+     rev linkrev                                   nodeid p1-rev                                p1-nodeid                                p2-nodeid
+       0       0 a0c8bcbbb45c63b90b70ad007bf38961f64f2af0     -1 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
+       1       1 57faf8a737ae7faf490582941a82319ba6529dca      0 a0c8bcbbb45c63b90b70ad007bf38961f64f2af0 0000000000000000000000000000000000000000
+       2       2 a35b103209548032201c16c7688cb2657f037a38      1 57faf8a737ae7faf490582941a82319ba6529dca 0000000000000000000000000000000000000000
   $ hg debugindex a
      rev linkrev       nodeid    p1-nodeid    p2-nodeid
        0       0 b789fdd96dc2 000000000000 000000000000
   $ hg debugindex --debug a
-     rev linkrev                                   nodeid                                p1-nodeid                                p2-nodeid
-       0       0 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
+     rev linkrev                                   nodeid p1-rev                                p1-nodeid                                p2-nodeid
+       0       0 b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3     -1 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
 
 debugdelta chain basic output
 
diff --git a/tests/test-sidedata.t b/tests/test-sidedata.t
--- a/tests/test-sidedata.t
+++ b/tests/test-sidedata.t
@@ -41,16 +41,16 @@ Check data can be written/read from side
    entry-0002 size 32
 
   $ hg debug-revlog-index --verbose -c
-     rev linkrev       nodeid    p1-nodeid    p2-nodeid
-       0       0 7049e48789d7 000000000000 000000000000
-       1       1 2707720c6597 7049e48789d7 000000000000
-       2       2 40f977031323 2707720c6597 000000000000
+     rev linkrev       nodeid p1-rev    p1-nodeid    p2-nodeid
+       0       0 7049e48789d7     -1 000000000000 000000000000
+       1       1 2707720c6597      0 7049e48789d7 000000000000
+       2       2 40f977031323      1 2707720c6597 000000000000
 
   $ hg debug-revlog-index --verbose -m
-     rev linkrev       nodeid    p1-nodeid    p2-nodeid
-       0       0 b85d294330e3 000000000000 000000000000
-       1       1 1a0aec305c63 b85d294330e3 000000000000
-       2       2 104258a4f75f 1a0aec305c63 000000000000
+     rev linkrev       nodeid p1-rev    p1-nodeid    p2-nodeid
+       0       0 b85d294330e3     -1 000000000000 000000000000
+       1       1 1a0aec305c63      0 b85d294330e3 000000000000
+       2       2 104258a4f75f      1 1a0aec305c63 000000000000
 
 Check upgrade behavior
 ======================