diff --git a/configs/karura.yml b/configs/karura.yml
index ca15a44..5ca5b50 100644
--- a/configs/karura.yml
+++ b/configs/karura.yml
@@ -42,4 +42,3 @@ parachains:
   nodes:
   - flags:
     - --alice
-
diff --git a/configs/kusama.yml b/configs/kusama.yml
index fd7fdd4..1eaabb9 100644
--- a/configs/kusama.yml
+++ b/configs/kusama.yml
@@ -6,6 +6,17 @@ relaychain:
       config:
         validation_upgrade_frequency: 1
         validation_upgrade_delay: 1
+    # enable hrmp channels after: https://github.com/paritytech/polkadot/pull/4324
+    # hrmp:
+    #   preopenHrmpChannels:
+    #     - sender: 2000
+    #       recipient: 2001
+    #       maxCapacity: 8
+    #       maxMessageSize: 102400
+    #     - sender: 2001
+    #       recipient: 2000
+    #       maxCapacity: 8
+    #       maxMessageSize: 102400
   env:
     RUST_LOG: parachain::candidate-backing=trace,parachain::candidate-selection=trace,parachain::pvf=trace,parachain::collator-protocol=trace,parachain::provisioner=trace
   flags:
diff --git a/src/index.ts b/src/index.ts
index c86104a..7d2b938 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -177,6 +177,16 @@ const generateRelaychainGenesisFile = (config: Config, path: string, output: str
 
   // additional patches
   if (config.relaychain.runtimeGenesisConfig) {
+    const hrmp = config.relaychain.runtimeGenesisConfig.hrmp;
+    if (hrmp) {
+      hrmp.preopenHrmpChannels = hrmp.preopenHrmpChannels.map((channel) => {
+        if (!Array.isArray(channel)) {
+          return [channel.sender, channel.recipient, channel.maxCapacity, channel.maxMessageSize];
+        } else {
+          return channel;
+        }
+      });
+    }
     _.merge(runtime, config.relaychain.runtimeGenesisConfig);
   }
 
diff --git a/src/types.ts b/src/types.ts
index 951f1d1..cb1a3e8 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -11,6 +11,9 @@ export interface RelayChain {
   nodes: Node[];
   runtimeGenesisConfig: {
     configuration: { config: { [index: string]: string | number } };
+    hrmp?: {
+      preopenHrmpChannels: HrmpChannelsConfig[];
+    };
   };
 }
 
@@ -68,3 +71,12 @@ export interface DockerNode {
     };
   };
 }
+
+export type HrmpChannelsConfig =
+  | {
+      sender: number;
+      recipient: number;
+      maxCapacity: number;
+      maxMessageSize: number;
+    }
+  | [number, number, number, number];