diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -1058,8 +1058,8 @@
     data[b'nb-revs'] = len(all)
     data[b'nb-revs-common'] = len(common)
     data[b'nb-revs-missing'] = len(missing)
-    data[b'nb-missing-heads'] = len(roots_missing)
-    data[b'nb-missing-roots'] = len(heads_missing)
+    data[b'nb-missing-heads'] = len(heads_missing)
+    data[b'nb-missing-roots'] = len(roots_missing)
     data[b'nb-ini_und'] = len(initial_undecided)
     data[b'nb-ini_und-heads'] = len(heads_initial_undecided)
     data[b'nb-ini_und-roots'] = len(roots_initial_undecided)