diff --git a/.travis.yml b/.travis.yml
index ca52bf2681..fcea6cb174 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,6 +24,7 @@ notifications:
 env:
   global:
     - PYTHONWARNINGS=always::DeprecationWarning
+    - CRYPTOGRAPHY_ALLOW_OPENSSL_102=1
 
     - PYPI_USERNAME=urllib3
     # PYPI_PASSWORD is set in Travis control panel.
diff --git a/ci/install.sh b/ci/install.sh
index adda3d13cb..20bd477c6c 100755
--- a/ci/install.sh
+++ b/ci/install.sh
@@ -8,7 +8,7 @@ set -exo pipefail
 # we're in one of the Travis Python 2 sessions and sets up the Python 3 install
 # for Nox.
 if ! python3 -m pip --version; then
-    curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
+    curl https://bootstrap.pypa.io/3.5/get-pip.py -o get-pip.py
     sudo python3 get-pip.py
     # https://github.com/theacodes/nox/issues/328
     sudo python3 -m pip install nox==2019.11.9
diff --git a/src/urllib3/connection.py b/src/urllib3/connection.py
index d2d456fb3c..9066e6ade4 100644
--- a/src/urllib3/connection.py
+++ b/src/urllib3/connection.py
@@ -215,7 +215,7 @@ def putrequest(self, method, url, *args, **kwargs):
 
     def putheader(self, header, *values):
         """"""
-        if SKIP_HEADER not in values:
+        if not any(isinstance(v, str) and v == SKIP_HEADER for v in values):
             _HTTPConnection.putheader(self, header, *values)
         elif six.ensure_str(header.lower()) not in SKIPPABLE_HEADERS:
             raise ValueError(