diff --git a/tox.ini b/tox.ini
index 62547b3df..6c7150d9f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,7 +20,7 @@ passenv = TAHOE_LAFS_* PIP_* SUBUNITREPORTER_* USERPROFILE HOMEDRIVE HOMEPATH
 # available to those systems.  Installing it ahead of time (with pip) avoids
 # this problem.
 deps =
-     pip<19
+     pip>8.1.1,<19
      certifi
      subunitreporter
 # We add usedevelop=True for speed, and extras=test to get things like "mock"