diff --git a/hgext/sparse.py b/hgext/sparse.py
--- a/hgext/sparse.py
+++ b/hgext/sparse.py
@@ -110,6 +110,8 @@ def uisetup(ui):
     _setupcommit(ui)
 
 def extsetup(ui):
+    sparse.enabled = True
+
     _setupclone(ui)
     _setuplog(ui)
     _setupadd(ui)
diff --git a/mercurial/sparse.py b/mercurial/sparse.py
--- a/mercurial/sparse.py
+++ b/mercurial/sparse.py
@@ -12,6 +12,11 @@ from . import (
     error,
 )
 
+# Whether sparse features are enabled. This variable is intended to be
+# temporary to facilitate porting sparse to core. It should eventually be
+# a per-repo option, possibly a repo requirement.
+enabled = False
+
 def parseconfig(ui, raw):
     """Parse sparse config file content.