diff --git a/.arcconfig b/.arcconfig
--- a/.arcconfig
+++ b/.arcconfig
@@ -1,5 +1,6 @@
 {
     "conduit_uri": "https://phab.mercurial-scm.org/api",
+    "phabricator.uri": "https://phab.mercurial-scm.org/",
     "repository.callsign": "HG",
     "arc.land.onto.default": "@",
     "base": "hg:.^"
diff --git a/hgext/phabricator.py b/hgext/phabricator.py
--- a/hgext/phabricator.py
+++ b/hgext/phabricator.py
@@ -178,11 +178,16 @@
     except IOError:
         pass
 
+    cfg = util.sortdict()
+
     if b"repository.callsign" in arcconfig:
-        ui.applyconfig(
-            {(b"phabricator", b"callsign"): arcconfig[b"repository.callsign"]},
-            source=wdirvfs.join(b".arcconfig"),
-        )
+        cfg[(b"phabricator", b"callsign")] = arcconfig[b"repository.callsign"]
+
+    if b"phabricator.uri" in arcconfig:
+        cfg[(b"phabricator", b"url")] = arcconfig[b"phabricator.uri"]
+
+    if cfg:
+        ui.applyconfig(cfg, source=wdirvfs.join(b".arcconfig"))
 
     return orig(ui, wdirvfs, hgvfs, requirements) or result  # Load .hg/hgrc
 
diff --git a/tests/test-phabricator.t b/tests/test-phabricator.t
--- a/tests/test-phabricator.t
+++ b/tests/test-phabricator.t
@@ -228,8 +228,8 @@
   $ mv .hg/hgrc .hg/hgrc.bak
   $ hg config phabricator --debug
   read config from: */.hgrc (glob)
-  */.hgrc:*: phabricator.url=global (glob)
   $TESTTMP/repo/.arcconfig: phabricator.callsign=HG
+  $TESTTMP/repo/.arcconfig: phabricator.url=https://phab.mercurial-scm.org/
 
 But it doesn't override local config
   $ cat >> .hg/hgrc << EOF