@@ -216,6 +216,9 @@ class Channel {
   }
 
   subscribe(subscription) {
+    // Validate before activation so that an invalid subscription does not
+    // leave the channel active without a subscriber (nodejs/node#65313).
+    validateFunction(subscription, "subscription");
     markActive(this);
     this.subscribe(subscription);
   }
 
@@ -0,0 +1,33 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+
+import dc from "node:diagnostics_channel";
+import { assert, assertFalse, assertThrows } from "@std/assert";
+
+Deno.test("[diagnostics_channel] an invalid subscription does not activate the channel", () => {
+  const name = "diagnostics-channel-invalid-subscription";
+  const channel = dc.channel(name);
+
+  assertThrows(
+    // deno-lint-ignore no-explicit-any
+    () => dc.subscribe(name, null as any),
+    TypeError,
+    'The "subscription" argument must be of type function',
+  );
+  assertFalse(channel.hasSubscribers);
+  assertFalse(dc.hasSubscribers(name));
+
+  assertThrows(
+    // deno-lint-ignore no-explicit-any
+    () => channel.subscribe(null as any),
+    TypeError,
+    'The "subscription" argument must be of type function',
+  );
+  assertFalse(channel.hasSubscribers);
+  assertFalse(dc.hasSubscribers(name));
+
+  const subscriber = () => {};
+  channel.subscribe(subscriber);
+  assert(channel.hasSubscribers);
+  assert(channel.unsubscribe(subscriber));
+  assertFalse(channel.hasSubscribers);
+});
Original file line number	Diff line number	Diff line change
`@@ -216,6 +216,9 @@ class Channel {`
`216`	`216`	`}`
`217`	`217`
`218`	`218`	`subscribe(subscription) {`
	`219`	`+ // Validate before activation so that an invalid subscription does not`
	`220`	`+ // leave the channel active without a subscriber (nodejs/node#65313).`
	`221`	`+ validateFunction(subscription, "subscription");`
`219`	`222`	`markActive(this);`
`220`	`223`	`this.subscribe(subscription);`
`221`	`224`	`}`