diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 083c884..4a4d690 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,8 +8,6 @@ jobs:
       fail-fast: false
       matrix:
         python:
-          - py27
-          - py36
           - py37
         httplib:
           - default
diff --git a/tox.ini b/tox.ini
index 7e5545e..45e5a9b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = {py27,py36,py37}-{default,fido}, {py27,py36,py37}-fido-requests2dot17, mypy, pre-commit
+envlist = {py37}-{default,fido}, {py27,py37}-fido-requests2dot17, mypy, pre-commit
 
 [testenv]
 deps =
@@ -37,6 +37,8 @@ deps =
     Twisted<21
     # since we run in py 2.7 compatible mode, swagger-spec-validator>=3.0.0 causes syntax errors
     swagger-spec-validator<3.0.0
+    # so does yelp-bytes < 0.4.0
+    yelp-bytes==0.4.0
     -rrequirements-dev.txt
     .[fido]
     mypy==0.790