diff --git a/liteeth/core/udp.py b/liteeth/core/udp.py
index b00f26c..bc4d9ec 100644
--- a/liteeth/core/udp.py
+++ b/liteeth/core/udp.py
@@ -45,7 +45,7 @@ class LiteEthUDPCrossbar(LiteEthCrossbar):
 
         # tx
         tx_stream = user_port.sink
-        if cd is not "sys":
+        if cd != "sys":
             tx_cdc = stream.AsyncFIFO(eth_udp_user_description(user_port.dw), 4)
             tx_cdc = ClockDomainsRenamer({"write": cd, "read": "sys"})(tx_cdc)
             self.submodules += tx_cdc
@@ -69,7 +69,7 @@ class LiteEthUDPCrossbar(LiteEthCrossbar):
             self.submodules += rx_converter
             self.comb += rx_stream.connect(rx_converter.sink)
             rx_stream = rx_converter.source
-        if cd is not "sys":
+        if cd != "sys":
             rx_cdc = stream.AsyncFIFO(eth_udp_user_description(user_port.dw), 4)
             rx_cdc = ClockDomainsRenamer({"write": "sys", "read": cd})(rx_cdc)
             self.submodules += rx_cdc
diff --git a/test/model/dumps.py b/test/model/dumps.py
index bfcbc03..e9ea8f2 100644
--- a/test/model/dumps.py
+++ b/test/model/dumps.py
@@ -9,7 +9,7 @@ import re
 # Helpers ------------------------------------------------------------------------------------------
 
 def format_dump(dump):
-    return [int(s, 16) for s in re.split(r'[;,\s\n]\s*', dump) if s is not ""]
+    return [int(s, 16) for s in re.split(r'[;,\s\n]\s*', dump) if s != ""]
 
 
 def verify_packet(packet, infos):