diff --git a/adb_shell/transport/base_transport.py b/adb_shell/transport/base_transport.py
index 4ab3849..a5552b4 100644
--- a/adb_shell/transport/base_transport.py
+++ b/adb_shell/transport/base_transport.py
@@ -43,7 +43,7 @@ def connect(self, transport_timeout_s):
 
         Parameters
         ----------
-        transport_timeout_s : float
+        transport_timeout_s : float, None
             A connection timeout
 
         """
@@ -56,7 +56,7 @@ def bulk_read(self, numbytes, transport_timeout_s):
         ----------
         numbytes : int
             The maximum amount of data to be received
-        transport_timeout_s : float
+        transport_timeout_s : float, None
             A timeout for the read operation
 
         Returns
@@ -74,7 +74,7 @@ def bulk_write(self, data, transport_timeout_s):
         ----------
         data : bytes
             The data to be sent
-        transport_timeout_s : float
+        transport_timeout_s : float, None
             A timeout for the write operation
 
         Returns