diff --git a/src/client/index.ts b/src/client/index.ts
index 97e6ee07..2c08bcc0 100644
--- a/src/client/index.ts
+++ b/src/client/index.ts
@@ -244,6 +244,10 @@ export class Client<
         // No specific capability required for initialized
         break;
 
+      case "notifications/cancelled":
+        // Cancellation notifications are always allowed
+        break;
+
       case "notifications/progress":
         // Progress notifications are always allowed
         break;
diff --git a/src/server/index.ts b/src/server/index.ts
index 29a3207a..d15ad3c0 100644
--- a/src/server/index.ts
+++ b/src/server/index.ts
@@ -157,6 +157,10 @@ export class Server<
         }
         break;
 
+      case "notifications/cancelled":
+        // Cancellation notifications are always allowed
+        break;
+
       case "notifications/progress":
         // Progress notifications are always allowed
         break;