diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -373,7 +373,7 @@ def update(repo, node, branchmerge, forc
                 if wc.files() or wc.deleted():
                     raise util.Abort(_("crosses branches (use 'hg merge' or "
                                        "'hg update -C' to discard changes)"))
-                raise util.Abort(_("crosses branches (use 'hg merge'"
+                raise util.Abort(_("crosses branches (use 'hg merge' "
                                    "or 'hg update -C')"))
             elif wc.files() or wc.deleted():
                 raise util.Abort(_("crosses named branches (use "
diff --git a/tests/test-merge5.out b/tests/test-merge5.out
--- a/tests/test-merge5.out
+++ b/tests/test-merge5.out
@@ -4,4 +4,4 @@ created new head
 % should abort
 abort: crosses branches (use 'hg merge' or 'hg update -C' to discard changes)
 % should succeed
-abort: crosses branches (use 'hg merge'or 'hg update -C')
+abort: crosses branches (use 'hg merge' or 'hg update -C')