diff --git a/mitmproxy/certs.py b/mitmproxy/certs.py
index 0e441efed..c5f930e1f 100644
--- a/mitmproxy/certs.py
+++ b/mitmproxy/certs.py
@@ -480,10 +480,8 @@ class SSLCert(serializable.Serializable):
                 except PyAsn1Error:
                     continue
                 for i in dec[0]:
-                    if i[0] is None and isinstance(i[1], univ.OctetString) and not isinstance(i[1], char.IA5String):
-                        # This would give back the IP address: b'.'.join([str(e).encode() for e in i[1].asNumbers()])
-                        continue
-                    else:
+                    if i[0].hasValue():
                         e = i[0].asOctets()
-                    altnames.append(e)
+                        altnames.append(e)
+
         return altnames
diff --git a/setup.py b/setup.py
index 433635e4d..02dab61fd 100644
--- a/setup.py
+++ b/setup.py
@@ -73,7 +73,7 @@ setup(
         "kaitaistruct>=0.7, <0.8",
         "ldap3>=2.2.0, <2.3",
         "passlib>=1.6.5, <1.8",
-        "pyasn1>=0.1.9, <0.3",
+        "pyasn1>=0.3.1, <0.4",
         "pyOpenSSL>=17.2,<17.3",
         "pyparsing>=2.1.3, <2.3",
         "pyperclip>=1.5.22, <1.6",