diff --git a/setup.py b/setup.py
index 357b9cd41..02624c842 100644
--- a/setup.py
+++ b/setup.py
@@ -75,13 +75,7 @@ install_requires = [
     #   leftover timers)
     # * Twisted-16.4.0 introduces `python -m twisted.trial` which is needed
     #   for coverage testing
-
-    # * Twisted 16.6.0 drops the undesirable gmpy dependency from the conch
-    #   extra, letting us use that extra instead of trying to duplicate its
-    #   dependencies here.  Twisted[conch] >18.7 introduces a dependency on
-    #   bcrypt.  It is nice to avoid that if the user ends up with an older
-    #   version of Twisted.  That's hard to express except by using the extra.
-    "Twisted[tls,conch] >= 16.6.0",
+    "Twisted[tls] >= 16.4.0",
 
     # We need Nevow >= 0.11.1 which can be installed using pip.
     "Nevow >= 0.11.1",
@@ -108,6 +102,23 @@ setup_requires = [
     'setuptools >= 28.8.0',  # for PEP-440 style versions
 ]
 
+sftp_requires = [
+    # * Twisted 16.6.0 drops the undesirable gmpy dependency from the conch
+    #   extra, letting us use that extra instead of trying to duplicate its
+    #   dependencies here.  Twisted[conch] >18.7 introduces a dependency on
+    #   bcrypt.  It is nice to avoid that if the user ends up with an older
+    #   version of Twisted.  That's hard to express except by using the extra.
+    "twisted[conch] >= 16.6.0",
+]
+
+tor_requires = [
+    "foolscap[tor] >= 0.12.5",
+]
+
+i2p_requires = [
+    "foolscap[i2p] >= 0.12.6",
+]
+
 if len(sys.argv) > 1 and sys.argv[1] == '--fakedependency':
     del sys.argv[1]
     install_requires += ["fakedependency >= 1.0.0"]
@@ -330,10 +341,6 @@ setup(name="tahoe-lafs", # also set in __init__.py
               "coverage",
               "mock",
               "tox",
-              "foolscap[tor] >= 0.12.5",
-              "txtorcon >= 0.17.0", # in case pip's resolver doesn't work
-              "foolscap[i2p] >= 0.12.6",
-              "txi2p >= 0.3.2", # in case pip's resolver doesn't work
               "pytest",
               "pytest-twisted",
               "hypothesis >= 3.6.1",
@@ -341,15 +348,10 @@ setup(name="tahoe-lafs", # also set in __init__.py
               "towncrier",
               "testtools",
               "fixtures",
-          ],
-          "tor": [
-              "foolscap[tor] >= 0.12.5",
-              "txtorcon >= 0.17.0", # in case pip's resolver doesn't work
-          ],
-          "i2p": [
-              "foolscap[i2p] >= 0.12.6",
-              "txi2p >= 0.3.2", # in case pip's resolver doesn't work
-          ],
+          ] + sftp_requires + tor_requires + i2p_requires,
+          "sftp": sftp_requires,
+          "tor": tor_requires,
+          "i2p": i2p_requires,
       },
       package_data={"allmydata.web": ["*.xhtml",
                                       "static/*.js", "static/*.png", "static/*.css",