diff --git a/tests/test_x509_cert.py b/tests/test_x509_cert.py
index cb5b6cdf..a9ffdc4d 100644
--- a/tests/test_x509_cert.py
+++ b/tests/test_x509_cert.py
@@ -13,13 +13,13 @@ class MyTests(unittest.TestCase):
         with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-ca-cert.der'), 'rb') as f:
             self.x509_ca_cert = f.read()
 
-        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-cert-and-key.pem'), 'rb') as f:
+        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-cert-and-key.pem'), 'r', encoding='utf-8') as f:
             self.x509_cert_and_key_pem = f.read()
 
-        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-letsencrypt.pem'), 'rb') as f:
+        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-letsencrypt.pem'), 'r', encoding='utf-8') as f:
             self.x509_letsencrypt = f.read()
 
-        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-multi-cert.pem'), 'rb') as f:
+        with open(os.path.join(THIS_DIR, os.pardir, 'tests/fixtures/generic/x509-multi-cert.pem'), 'r', encoding='utf-8') as f:
             self.x509_multi_cert = f.read()
 
         # output