diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -670,9 +670,9 @@ Example for ``~/.hgrc``::
     Enable or disable the "generaldelta" repository format which improves
     repository compression by allowing "revlog" to store delta against arbitrary
     revision instead of the previous stored one. This provides significant
-    improvement for repositories with branches. Disabling this option ensures that
-    the on-disk format of newly created repository will be compatible with
-    Mercurial before version 1.9.
+    improvement for repositories with branches. Enabled by default. Disabling
+    this option ensures that the on-disk format of newly created repository will
+    be compatible with Mercurial before version 1.9.
 
 ``usestore``
     Enable or disable the "store" repository format which improves
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1176,7 +1176,7 @@ def gdinitconfig(ui):
     """
     # experimental config: format.generaldelta
     return (ui.configbool('format', 'generaldelta', False)
-            or ui.configbool('format', 'usegeneraldelta', False))
+            or ui.configbool('format', 'usegeneraldelta', True))
 
 def gddeltaconfig(ui):
     """helper function to know if incoming delta should be optimised