diff --git a/.circleci/config.yml b/.circleci/config.yml
index c3094b9..fa7691e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -48,24 +48,30 @@ jobs:
       - image: circleci/python:3.6
         environment:
           TOXENV: lint
-  py36-test:
+  py36-core:
     <<: *common
     docker:
       - image: circleci/python:3.6
         environment:
-          TOXENV: py36-test
-  py37-test:
+          TOXENV: py36-core
+  py37-core:
     <<: *common
     docker:
       - image: circleci/python:3.7
         environment:
-          TOXENV: py37-test
-
+          TOXENV: py37-core
+  pypy3-core:
+    <<: *common
+    docker:
+      - image: pypy
+        environment:
+          TOXENV: pypy3-core
 workflows:
   version: 2
   test:
     jobs:
       - docs
       - lint
-      - py36-test
-      - py37-test
+      - py36-core
+      - py37-core
+      - pypy3-core
diff --git a/libp2p/network/connection/raw_connection.py b/libp2p/network/connection/raw_connection.py
index 55b47ef..4f01b12 100644
--- a/libp2p/network/connection/raw_connection.py
+++ b/libp2p/network/connection/raw_connection.py
@@ -53,5 +53,6 @@ class RawConnection(IRawConnection):
 
     async def close(self) -> None:
         self.writer.close()
-        if sys.version_info[0:2] > (3, 6):
-            await self.writer.wait_closed()
+        if sys.version_info < (3, 7):
+            return
+        await self.writer.wait_closed()
diff --git a/libp2p/tools/factories.py b/libp2p/tools/factories.py
index 5e22313..5c9c310 100644
--- a/libp2p/tools/factories.py
+++ b/libp2p/tools/factories.py
@@ -1,6 +1,8 @@
 import asyncio
 from typing import Any, AsyncIterator, Dict, Tuple, cast
 
+# NOTE: import ``asynccontextmanager`` from ``contextlib`` when support for python 3.6 is dropped.
+from async_generator import asynccontextmanager
 import factory
 
 from libp2p import generate_new_rsa_identity, generate_peer_id_from
@@ -32,12 +34,6 @@ from .constants import (
 )
 from .utils import connect, connect_swarm
 
-try:
-    from contextlib import asynccontextmanager
-except ImportError:
-    # NOTE: mypy complains about a duplicate import without the following ``# type: ignore``
-    from async_generator import asynccontextmanager  # type: ignore
-
 
 def initialize_peerstore_with_our_keypair(self_id: ID, key_pair: KeyPair) -> PeerStore:
     peer_store = PeerStore()
@@ -177,7 +173,7 @@ async def host_pair_factory(is_secure: bool) -> Tuple[BasicHost, BasicHost]:
     return hosts[0], hosts[1]
 
 
-@asynccontextmanager
+@asynccontextmanager  # type: ignore
 async def pair_of_connected_hosts(
     is_secure: bool = True
 ) -> AsyncIterator[Tuple[BasicHost, BasicHost]]:
diff --git a/libp2p/transport/tcp/tcp.py b/libp2p/transport/tcp/tcp.py
index c27de0e..f5c2aa4 100644
--- a/libp2p/transport/tcp/tcp.py
+++ b/libp2p/transport/tcp/tcp.py
@@ -54,9 +54,11 @@ class TCPListener(IListener):
         if self.server is None:
             return
         self.server.close()
-        if sys.version_info[0:2] > (3, 6):
-            await self.server.wait_closed()
+        server = self.server
         self.server = None
+        if sys.version_info < (3, 7):
+            return
+        await server.wait_closed()
 
 
 class TCP(ITransport):
diff --git a/setup.py b/setup.py
index 35b17bf..56a6bf2 100644
--- a/setup.py
+++ b/setup.py
@@ -59,7 +59,7 @@ install_requires = [
     "coincurve>=10.0.0,<11.0.0",
     "pynacl==1.3.0",
     "dataclasses>=0.7, <1;python_version<'3.7'",
-    "async_generator==1.10;python_version<'3.7'",
+    "async_generator==1.10",
 ]
 
 
@@ -96,6 +96,7 @@ setup(
         "License :: OSI Approved :: Apache Software License",
         "Natural Language :: English",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
     ],
     platforms=["unix", "linux", "osx"],
diff --git a/tests_interop/conftest.py b/tests_interop/conftest.py
index 3fcc74f..08df614 100644
--- a/tests_interop/conftest.py
+++ b/tests_interop/conftest.py
@@ -151,8 +151,9 @@ class DaemonStream(ReadWriteCloser):
 
     async def close(self) -> None:
         self.writer.close()
-        if sys.version_info[0:2] > (3, 6):
-            await self.writer.wait_closed()
+        if sys.version_info < (3, 7):
+            return
+        await self.writer.wait_closed()
 
     async def read(self, n: int = -1) -> bytes:
         return await self.reader.read(n)
diff --git a/tox.ini b/tox.ini
index a482e70..21f4643 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,8 +3,7 @@
 # TODO: consider pypy3 support
 [tox]
 envlist =
-    py36-test
-    py37-test
+    py{36,37}-test
     py37-interop
     lint
     docs