diff --git a/peewee_async/pool.py b/peewee_async/pool.py
index e8586bb..e3988d4 100644
--- a/peewee_async/pool.py
+++ b/peewee_async/pool.py
@@ -2,7 +2,7 @@
 import asyncio
 from typing import Any, Optional, cast
 
-from .utils import aiopg, aiomysql, PoolProtocol, ConnectionProtocol, format_dsn, psycopg, psycopg_pool
+from .utils import aiopg, aiomysql, ConnectionProtocol, format_dsn, psycopg, psycopg_pool
 
 
 class PoolBackend(metaclass=abc.ABCMeta):
@@ -10,7 +10,7 @@ class PoolBackend(metaclass=abc.ABCMeta):
     """
 
     def __init__(self, *, database: str, **kwargs: Any) -> None:
-        self.pool: Optional[PoolProtocol] = None
+        self.pool: Optional[Any] = None
         self.database = database
         self.connect_params = kwargs
         self._connection_lock = asyncio.Lock()
@@ -23,11 +23,13 @@ def is_connected(self) -> bool:
 
     @property
     def min_size(self) -> int:
-        return self.pool.minsize
+        assert self.pool is not None, "Pool is not connected"
+        return cast(int, self.pool.minsize)
 
     @property
     def max_size(self) -> int:
-        return self.pool.maxsize
+        assert self.pool is not None, "Pool is not connected"
+        return cast(int, self.pool.maxsize)
 
     def has_acquired_connections(self) -> bool:
         if self.pool is not None:
@@ -45,7 +47,7 @@ async def acquire(self) -> ConnectionProtocol:
         if self.pool is None:
             await self.connect()
         assert self.pool is not None, "Pool is not connected"
-        return await self.pool.acquire()
+        return cast(ConnectionProtocol, await self.pool.acquire())
 
     async def release(self, conn: ConnectionProtocol) -> None:
         """Release connection to pool.
@@ -76,12 +78,9 @@ async def create(self) -> None:
         """
         if "connect_timeout" in self.connect_params:
             self.connect_params['timeout'] = self.connect_params.pop("connect_timeout")
-        self.pool = cast(
-            PoolProtocol,
-            await aiopg.create_pool(
-                database=self.database,
-                **self.connect_params
-            )
+        self.pool = await aiopg.create_pool(
+            database=self.database,
+            **self.connect_params
         )
 
 
@@ -117,7 +116,7 @@ async def create(self) -> None:
 
     def has_acquired_connections(self) -> bool:
         if self.pool is not None:
-            return self.pool._nconns - self.pool._num_pool > 0
+            return bool(self.pool.nconns - self.pool._num_pool > 0)
         return False
 
     async def acquire(self) -> ConnectionProtocol:
@@ -126,7 +125,7 @@ async def acquire(self) -> ConnectionProtocol:
         if self.pool is None:
             await self.connect()
         assert self.pool is not None, "Pool is not connected"
-        return await self.pool.getconn()
+        return cast(ConnectionProtocol, await self.pool.getconn())
 
     async def release(self, conn: ConnectionProtocol) -> None:
         """Release connection to pool.
@@ -142,11 +141,13 @@ async def terminate(self) -> None:
 
     @property
     def min_size(self) -> int:
-        return self.pool.min_size
+        assert self.pool is not None, "Pool is not connected"
+        return cast(int, self.pool.min_size)
 
     @property
     def max_size(self) -> int:
-        return self.pool.max_size
+        assert self.pool is not None, "Pool is not connected"
+        return cast(int, self.pool.max_size)
 
 
 class MysqlPoolBackend(PoolBackend):
@@ -156,9 +157,6 @@ class MysqlPoolBackend(PoolBackend):
     async def create(self) -> None:
         """Create connection pool asynchronously.
         """
-        self.pool = cast(
-            PoolProtocol,
-            await aiomysql.create_pool(
-                db=self.database, **self.connect_params
-            ),
+        self.pool = await aiomysql.create_pool(
+            db=self.database, **self.connect_params
         )
diff --git a/peewee_async/utils.py b/peewee_async/utils.py
index bcf3d87..1d17da1 100644
--- a/peewee_async/utils.py
+++ b/peewee_async/utils.py
@@ -57,27 +57,6 @@ def cursor(
         ...
 
 
-class PoolProtocol(Protocol):
-
-    _used: Set[ConnectionProtocol]
-
-    @property
-    def closed(self) -> bool:
-        ...
-
-    async def acquire(self) -> ConnectionProtocol:
-        ...
-
-    def release(self, conn: ConnectionProtocol) -> None:
-        ...
-
-    def terminate(self) -> None:
-        ...
-
-    async def wait_closed(self) -> None:
-        ...
-
-
 FetchResults = Callable[[CursorProtocol], Awaitable[Any]]
 
 
diff --git a/tests/test_database.py b/tests/test_database.py
index cd862bd..aa2250d 100644
--- a/tests/test_database.py
+++ b/tests/test_database.py
@@ -86,8 +86,8 @@ async def test_connections_param(db_name: str) -> None:
     database = db_cls(**default_params)
     await database.aio_connect()
 
-    assert database.pool_backend.min_size == 2  # type: ignore
-    assert database.pool_backend.max_size == 3  # type: ignore
+    assert database.pool_backend.min_size == 2
+    assert database.pool_backend.max_size == 3
 
     await database.aio_close()