diff --git a/default.nix b/default.nix
index 47247993c937d7d3899c7667e9b22a3df8fe8f81..771b273f9da00b1eb1c18d4ec05e324d4c86bee9 100644
--- a/default.nix
+++ b/default.nix
@@ -64,7 +64,7 @@ in
         # the `.post999` looks weird enough that if someone really cares about
         # the version in use they will notice it and go searching for what's
         # going on and discover the real version specified by `src` below.
-        version = "1.17.0.post999";
+        version = "1.17.1.post999";
         # See https://github.com/DavHau/mach-nix/issues/190
         requirementsExtra =
           ''
diff --git a/nix/sources.json b/nix/sources.json
index 3107940ad6eb2e03ecd62262606c802987a8cdce..201b605f7c26ee02d24c5580abef13367d50730f 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -54,15 +54,15 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "tahoe-lafs": {
-        "branch": "master",
+        "branch": "3858.release-1.17.1",
         "description": "The Tahoe-LAFS decentralized secure filesystem.",
         "homepage": "https://tahoe-lafs.org/",
-        "owner": "tahoe-lafs",
+        "owner": "meejah",
         "repo": "tahoe-lafs",
-        "rev": "tahoe-lafs-1.17.0",
-        "sha256": "0vjq7g1lfjd16y0iwnfsccp5k3q3av7wllkyqbsyd877a29nibzi",
+        "rev": "f7477043c5025642ef0fbeb042310decb774bd01",
+        "sha256": "0vzl8xz4iwbq7d7saa6rimzgwj23s3vfgr3f428rbg0wp7dshs9s",
         "type": "tarball",
-        "url": "https://github.com/tahoe-lafs/tahoe-lafs/archive/tahoe-lafs-1.17.0.tar.gz",
+        "url": "https://github.com/meejah/tahoe-lafs/archive/f7477043c5025642ef0fbeb042310decb774bd01.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }
diff --git a/setup.cfg b/setup.cfg
index 768163ca8a71a5f9f8efc5f7020ad57bff10b28b..99a57fb165ca22ac3f1f97e160667f09e890bbe4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -45,7 +45,7 @@ install_requires =
     # Tahoe has no stable Python API but we use its Python API so there's
     # basically no wiggle room here.  We still use a (really tiny) range
     # because our Nix packaging provides a Tahoe-LAFS with a .postNNN version.
-    tahoe-lafs >=1.17.0,<1.17.1
+    tahoe-lafs >=1.17.1,<1.17.2
     treq
     pyutil
     prometheus-client