diff --git a/multicast_expert/os_multicast.py b/multicast_expert/os_multicast.py
index 3f93e4d..52d00e8 100644
--- a/multicast_expert/os_multicast.py
+++ b/multicast_expert/os_multicast.py
@@ -24,18 +24,15 @@ def iface_ip_to_name(iface_ip: str) -> str:
 
     # Go from IP to interface name using netifaces.  To do that, we have to iterate through
     # all of the machine's interfaces
-    iface_name: Optional[str] = None
     for interface in netifaces.interfaces():
-        addresses_at_each_level: Dict[int, List[Dict[str, str]]] = netifaces.ifaddresses(interface)
+        addresses_at_each_level: Dict[int, List[Dict[str, str]]] = netifaces.ifaddresses(interface)  # type: ignore[assignment]
         for address_family in [netifaces.AF_INET, NETIFACES_AF_INET6_CONSTANT]:
             if address_family in addresses_at_each_level:
                 for address in addresses_at_each_level[address_family]:
                     if address["addr"] == iface_ip:
-                        iface_name = interface
-                        return iface_name
+                        return interface
 
-    if iface_name is None:
-        raise KeyError("Could not find network address with local IP " + iface_ip)
+    raise KeyError("Could not find network address with local IP " + iface_ip)
 
 
 def iface_name_to_index(iface_name: str) -> int:
diff --git a/multicast_expert/utils.py b/multicast_expert/utils.py
index 7e059f2..a598056 100644
--- a/multicast_expert/utils.py
+++ b/multicast_expert/utils.py
@@ -29,6 +29,7 @@
 # maps indexed by socket.AF_INET6 instead of netifaces.AF_INET6.
 # https://github.com/SamuelYvon/netifaces-2/issues/24
 # I am assuming this will get fixed in its next release, 0.0.22.
+NETIFACES_AF_INET6_CONSTANT: int
 if is_windows and using_netifaces_2 and packaging.version.parse(importlib.metadata.version("netifaces2")) <= packaging.version.parse("0.0.21"):
     NETIFACES_AF_INET6_CONSTANT = socket.AF_INET6
 else:
@@ -78,7 +79,7 @@ def get_default_gateway_iface_ip_v6() -> Optional[str]:
     Get the IP address of the interface that connects to the default IPv6 gateway, if it
     can be determined.  If it cannot be determined, None is returned.
     """
-    return get_default_gateway_iface_ip(netifaces.AF_INET6)  # type: ignore[arg-type]
+    return get_default_gateway_iface_ip(socket.AF_INET6)
 
 
 def get_default_gateway_iface_ip_v4() -> Optional[str]:
@@ -86,15 +87,21 @@ def get_default_gateway_iface_ip_v4() -> Optional[str]:
     Get the IP address of the interface that connects to the default IPv4 gateway, if it
     can be determined.  If it cannot be determined, None is returned.
     """
-    return get_default_gateway_iface_ip(netifaces.AF_INET)  # type: ignore[arg-type]
+    return get_default_gateway_iface_ip(socket.AF_INET)
 
 
-def get_default_gateway_iface_ip(addr_family: netifaces.InterfaceType) -> Optional[str]:
+def get_default_gateway_iface_ip(addr_family: int) -> Optional[str]:
     """
     Get the IP address of the interface that connects to the default gateway of the given addr_family, if it
     can be determined.  If it cannot be determined, None is returned.
     """
 
+    # Convert from socket constant to netifaces constant
+    if addr_family == socket.AF_INET6:
+        netifaces_addr_family = NETIFACES_AF_INET6_CONSTANT
+    else:
+        netifaces_addr_family = netifaces.AF_INET
+
     if using_netifaces_2:
 
         # In netifaces 2, we get the default_gateway() function to more easily determine the default gateway
@@ -104,8 +111,8 @@ def get_default_gateway_iface_ip(addr_family: netifaces.InterfaceType) -> Option
             # Default gateway search not implemented on this platform
             return None
 
-        if addr_family in default_gateways:
-            default_gateway_iface = default_gateways[addr_family][1]  # element 1 is the iface name
+        if netifaces_addr_family in default_gateways:
+            default_gateway_iface = default_gateways[netifaces_addr_family][1]  # element 1 is the iface name
         else:
             return None
 
@@ -118,19 +125,19 @@ def get_default_gateway_iface_ip(addr_family: netifaces.InterfaceType) -> Option
 
         # If it can, it will identify one of those as the default gateway for traffic.
         # If not, return none.
-        if not "default" in gateways:
+        if not "default" in gateways:  # type: ignore[comparison-overlap]
             return None
-        if not addr_family in gateways["default"]:
+        if not netifaces_addr_family in gateways["default"]:  # type: ignore[comparison-overlap, index]
             return None
 
-        default_gateway = gateways["default"][addr_family]
+        default_gateway = gateways["default"][netifaces_addr_family]  # type: ignore[index]
         default_gateway_iface = default_gateway[1]  # element 1 is the iface name, per the docs
 
     # Now, use the interface name to get the IP address of that interface
     interface_addresses = netifaces.ifaddresses(default_gateway_iface)
-    if addr_family not in interface_addresses:
+    if netifaces_addr_family not in interface_addresses:
         return None
-    return interface_addresses[addr_family][0]["addr"]
+    return interface_addresses[netifaces_addr_family][0]["addr"]  # type: ignore[index]
 
 
 def validate_mcast_ip(mcast_ip: str, addr_family: int) -> None: