diff --git a/lib/eth/chain.rb b/lib/eth/chain.rb
index 7be82402..8ca0b28f 100644
--- a/lib/eth/chain.rb
+++ b/lib/eth/chain.rb
@@ -85,6 +85,8 @@ class ReplayProtectionError < StandardError; end
 
     # Chain ID for the geth private network preset.
     PRIVATE_GETH = 1337.freeze
+    MATIC = 137.freeze
+    MUMBAI = 80001.freeze
 
     # Indicates wether the given `v` indicates a legacy chain value
     # without EIP-155 replay protection.