diff --git a/hgext3rd/fbamend/revsets.py b/hgext3rd/fbamend/revsets.py
--- a/hgext3rd/fbamend/revsets.py
+++ b/hgext3rd/fbamend/revsets.py
@@ -35,28 +35,15 @@
     s.sort()
     return subset & s
 
-@revsetpredicate('successors(set)')
-def successors(repo, subset, x):
-    """Immediate successors for given set"""
-    # getsuccessors: lookup node by precursor
-    getsuccessors = repo.obsstore.successors.get
+@revsetpredicate('precursors(set)')
+@revsetpredicate('predecessors(set)')
+def predecessors(repo, subset, x):
+    """Immediate predecessors for given set"""
+    getpredecessors = repo.obsstore.predecessors.get
     def f(nodes):
         for n in nodes:
-            for m in getsuccessors(n, ()):
-                # m[0]: precursor, m[1]: successors
-                for n in m[1]:
-                    yield n
-    return _calculateset(repo, subset, x, f)
-
-@revsetpredicate('precursors(set)')
-def precursors(repo, subset, x):
-    """Immediate precursors for given set"""
-    # getsuccessors: lookup node by precursor
-    getprecursors = repo.obsstore.precursors.get
-    def f(nodes):
-        for n in nodes:
-            for m in getprecursors(n, ()):
-                # m[0]: precursor, m[1]: successors
+            for m in getpredecessors(n, ()):
+                # m[0]: predecessor, m[1]: successors
                 yield m[0]
     return _calculateset(repo, subset, x, f)
 
@@ -67,7 +54,8 @@
     return _calculateset(repo, subset, x, f)
 
 @revsetpredicate('allprecursors(set)')
-def allprecursors(repo, subset, x):
-    """All changesets which are precursors for given set, recursively"""
-    f = lambda nodes: obsutil.allprecursors(repo.obsstore, nodes)
+@revsetpredicate('allpredecessors(set)')
+def allpredecessors(repo, subset, x):
+    """All changesets which are predecessors for given set, recursively"""
+    f = lambda nodes: obsutil.allpredecessors(repo.obsstore, nodes)
     return _calculateset(repo, subset, x, f)
diff --git a/hgext3rd/fbamend/unamend.py b/hgext3rd/fbamend/unamend.py
--- a/hgext3rd/fbamend/unamend.py
+++ b/hgext3rd/fbamend/unamend.py
@@ -19,9 +19,9 @@
 cmdtable = {}
 command = registrar.command(cmdtable)
 
-def precursormarkers(ctx):
-    """obsolete marker marking this changeset as a successors"""
-    for data in ctx.repo().obsstore.precursors.get(ctx.node(), ()):
+def predecessormarkers(ctx):
+    """yields the obsolete markers marking the given changeset as a successor"""
+    for data in ctx.repo().obsstore.predecessors.get(ctx.node(), ()):
         yield obsutil.marker(ctx.repo(), data)
 
 @command('^unamend', [])
@@ -45,9 +45,9 @@
     curctx = repo['.']
 
     # identify the commit to which to unamend
-    markers = list(precursormarkers(curctx))
+    markers = list(predecessormarkers(curctx))
     if len(markers) != 1:
-        e = _("changeset must have one precursor, found %i precursors")
+        e = _("changeset must have one predecessor, found %i predecessors")
         raise error.Abort(e % len(markers))
 
     prednode = markers[0].prednode()
diff --git a/hgext3rd/inhibit.py b/hgext3rd/inhibit.py
--- a/hgext3rd/inhibit.py
+++ b/hgext3rd/inhibit.py
@@ -16,19 +16,19 @@
 
 def _obsoletedrevs(repo):
     """Redefine "obsolete()" revset. Previously, X is obsoleted if X appears as
-    a precursor in a marker. Now, X is obsoleted if X is a precursor in marker
-    M1, *and* is not a successor in marker M2 where M2.date >= M1.date.
+    a predecessor in a marker. Now, X is obsoleted if X is a predecessor in
+    marker M1, *and* is not a successor in marker M2 where M2.date >= M1.date.
 
     This allows undo to return to old hashes, and is correct as long as
     obsmarker is not exchanged.
     """
     getnode = repo.changelog.node
-    markersbysuccessor = repo.obsstore.precursors.get
-    markersbyprecursor = repo.obsstore.successors.get
+    markersbysuccessor = repo.obsstore.predecessors.get
+    markersbypredecessor = repo.obsstore.successors.get
     result = set()
     for r in obsolete._mutablerevs(repo):
         n = getnode(r)
-        m1s = markersbyprecursor(n)
+        m1s = markersbypredecessor(n)
         m2s = markersbysuccessor(n)
         if m1s:
             if m2s:
@@ -52,9 +52,9 @@
         if date is None:
             date = util.makedate()
     # if prec is a successor of an existing marker, make default date bigger so
-    # the old marker won't revive the precursor accidentally. This helps tests
+    # the old marker won't revive the predecessor accidentally. This helps tests
     # where date are always (0, 0)
-    markers = self.precursors.get(prec)
+    markers = self.predecessors.get(prec)
     if markers:
         maxdate = max(m[4] for m in markers)
         maxdate = (maxdate[0] + 1, maxdate[1])
@@ -68,7 +68,7 @@
         return False
 
 def _createmarkers(orig, repo, rels, *args, **kwargs):
-    # make precursor context unfiltered so parents() won't raise
+    # make predecessor context unfiltered so parents() won't raise
     unfi = repo.unfiltered()
     rels = [list(r) for r in rels]  # make mutable
     for r in rels:
@@ -109,7 +109,7 @@
     # to write X -> X to revive X.
     extensions.wrapfunction(obsolete.obsstore, 'create', _obsstorecreate)
 
-    # make createmarkers use unfiltered precursor ctx, workarounds an issue
+    # make createmarkers use unfiltered predecessor ctx, workarounds an issue
     # that prec.parents() may raise FilteredIndexError.
     # NOTE: should be fixed upstream once hash-preserving obsstore is a thing.
     extensions.wrapfunction(obsolete, 'createmarkers', _createmarkers)