diff --git a/hgext/rebase.py b/hgext/rebase.py
index c156bf947e261344eb0852d1156b56107c4b3510_aGdleHQvcmViYXNlLnB5..b91960aed018b7fbcc9648ec6e823a9b7626f0da_aGdleHQvcmViYXNlLnB5 100644
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -381,5 +381,5 @@
     if src:
         commonbase = repo[src].ancestor(repo[dest])
         if commonbase == repo[src]:
-            raise util.Abort(_('cannot rebase an ancestor'))
+            raise util.Abort(_('source is ancestor of destination'))
         if commonbase == repo[dest]:
@@ -385,5 +385,5 @@
         if commonbase == repo[dest]:
-            raise util.Abort(_('cannot rebase a descendant'))
+            raise util.Abort(_('source is descendant of destination'))
         source = repo[src].rev()
     else:
         if base:
@@ -392,8 +392,8 @@
             cwd = repo['.'].rev()
 
         if cwd == dest:
-            repo.ui.debug('already working on current\n')
+            repo.ui.debug('source and destination are the same\n')
             return None
 
         targetancestors = set(repo.changelog.ancestors(dest))
         if cwd in targetancestors:
@@ -396,8 +396,8 @@
             return None
 
         targetancestors = set(repo.changelog.ancestors(dest))
         if cwd in targetancestors:
-            repo.ui.debug('already working on the current branch\n')
+            repo.ui.debug('source is ancestor of destination\n')
             return None
 
         cwdancestors = set(repo.changelog.ancestors(cwd))
diff --git a/tests/test-rebase-scenario-global.out b/tests/test-rebase-scenario-global.out
index c156bf947e261344eb0852d1156b56107c4b3510_dGVzdHMvdGVzdC1yZWJhc2Utc2NlbmFyaW8tZ2xvYmFsLm91dA==..b91960aed018b7fbcc9648ec6e823a9b7626f0da_dGVzdHMvdGVzdC1yZWJhc2Utc2NlbmFyaW8tZ2xvYmFsLm91dA== 100644
--- a/tests/test-rebase-scenario-global.out
+++ b/tests/test-rebase-scenario-global.out
@@ -129,5 +129,5 @@
 
 % These will fail
 % E onto D - rebase onto an ancestor
-abort: cannot rebase a descendant
+abort: source is descendant of destination
 % D onto E - rebase onto a descendant
@@ -133,4 +133,4 @@
 % D onto E - rebase onto a descendant
-abort: cannot rebase an ancestor
+abort: source is ancestor of destination
 % E onto B - merge revision with both parents not in ancestors of target
 abort: cannot use revision 4 as base, result would have 3 parents