diff --git a/mercurial/obsutil.py b/mercurial/obsutil.py
--- a/mercurial/obsutil.py
+++ b/mercurial/obsutil.py
@@ -311,6 +311,7 @@
 DESCCHANGED = 1 << 0 # action changed the description
 USERCHANGED = 1 << 4 # the user changed
 DATECHANGED = 1 << 5 # the date changed
+BRANCHCHANGED = 1 << 6 # the branch changed
 
 def geteffectflag(relation):
     """ From an obs-marker relation, compute what changed between the
@@ -333,6 +334,10 @@
         if changectx.date() != source.date():
             effects |= DATECHANGED
 
+        # Check if branch has changed
+        if changectx.branch() != source.branch():
+            effects |= BRANCHCHANGED
+
     return effects
 
 def getobsoleted(repo, tr):
diff --git a/tests/test-obsmarkers-effectflag.t b/tests/test-obsmarkers-effectflag.t
--- a/tests/test-obsmarkers-effectflag.t
+++ b/tests/test-obsmarkers-effectflag.t
@@ -65,7 +65,7 @@
 check result
 
   $ hg debugobsolete --rev .
-  bd3db8264ceebf1966319f5df3be7aac6acd1a8e 14a01456e0574f0e0a0b15b2345486a6364a8d79 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '0', 'operation': 'amend', 'user': 'test'}
+  bd3db8264ceebf1966319f5df3be7aac6acd1a8e 14a01456e0574f0e0a0b15b2345486a6364a8d79 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '64', 'operation': 'amend', 'user': 'test'}
 
   $ hg up default
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
@@ -106,7 +106,7 @@
 check result
 
   $ hg debugobsolete --rev .
-  fad47e5bd78e6aa4db1b5a0a1751bc12563655ff a94e0fd5f1c81d969381a76eb0d37ce499a44fae 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '49', 'operation': 'amend', 'user': 'test'}
+  fad47e5bd78e6aa4db1b5a0a1751bc12563655ff a94e0fd5f1c81d969381a76eb0d37ce499a44fae 0 (Thu Jan 01 00:00:00 1970 +0000) {'ef1': '113', 'operation': 'amend', 'user': 'test'}
 
 rebase not touching the diff
 ----------------------------