diff --git a/web/src/compose_validate.js b/web/src/compose_validate.js
index 7b7eb3717f..e779733693 100644
--- a/web/src/compose_validate.js
+++ b/web/src/compose_validate.js
@@ -59,7 +59,26 @@ export function needs_subscribe_warning(user_id, stream_id) {
     return true;
 }
 
-function get_stream_id() {
+function get_stream_id_for_textarea($textarea) {
+    // Returns the stream ID, if any, associated with the textarea:
+    // The recipient of a message being edited, or the target
+    // recipient of a message being drafted in the compose box.
+    // Returns undefined if the appropriate context is a direct
+    // message conversation.
+    const is_in_editing_area = $textarea.closest(".message_row").length > 0;
+
+    if (is_in_editing_area) {
+        const stream_id_str = $textarea
+            .closest(".recipient_row")
+            .find(".message_header")
+            .attr("data-stream-id");
+        if (stream_id_str === undefined) {
+            // Direct messages don't have a data-stream-id.
+            return undefined;
+        }
+        return Number.parseInt(stream_id_str, 10);
+    }
+
     const stream_name = compose_state.stream_name();
 
     if (!stream_name) {
@@ -70,17 +89,19 @@ function get_stream_id() {
 }
 
 export function warn_if_private_stream_is_linked(linked_stream, $textarea) {
-    // For PMs, we currently don't warn about links to private
-    // streams, since you are specifically sharing the existence of
-    // the private stream with someone.  One could imagine changing
-    // this policy if user feedback suggested it was useful.
-    if (compose_state.get_message_type() !== "stream") {
-        return;
-    }
-    const stream_id = get_stream_id();
+    const stream_id = get_stream_id_for_textarea($textarea);
+
     if (!stream_id) {
-        // We have an invalid stream name, don't warn about this here as
-        // we show an error to the user when they try to send the message.
+        // There are two cases in which the `stream_id` will be
+        // omitted, and we want to exclude the warning banner:
+        //
+        // 1. We currently do not warn about links to private streams
+        // in direct messages; it would probably be an improvement to
+        // do so when one of the recipients is not subscribed.
+        //
+        // 2. If we have an invalid stream name, we do not warn about
+        // it here; we will show an error to the user when they try to
+        // send the message.
         return;
     }
 
@@ -118,10 +139,6 @@ export function warn_if_private_stream_is_linked(linked_stream, $textarea) {
 }
 
 export function warn_if_mentioning_unsubscribed_user(mentioned, $textarea) {
-    if (compose_state.get_message_type() !== "stream") {
-        return;
-    }
-
     // Disable for Zephyr mirroring realms, since we never have subscriber lists there
     if (page_params.realm_is_zephyr_mirror_realm) {
         return;
@@ -133,7 +150,7 @@ export function warn_if_mentioning_unsubscribed_user(mentioned, $textarea) {
         return; // don't check if @all/@everyone/@stream
     }
 
-    const stream_id = get_stream_id();
+    const stream_id = get_stream_id_for_textarea($textarea);
 
     if (!stream_id) {
         return;
diff --git a/web/tests/compose_validate.test.js b/web/tests/compose_validate.test.js
index f0137131a3..891d8be1c9 100644
--- a/web/tests/compose_validate.test.js
+++ b/web/tests/compose_validate.test.js
@@ -66,6 +66,15 @@ function test_ui(label, f) {
     });
 }
 
+function stub_message_row($textarea) {
+    const $stub = $.create("message_row_stub");
+    $textarea.closest = (selector) => {
+        assert.equal(selector, ".message_row");
+        $stub.length = 0;
+        return $stub;
+    };
+}
+
 test_ui("validate_stream_message_address_info", ({mock_template}) => {
     mock_banners();
     const sub = {
@@ -622,6 +631,7 @@ test_ui("needs_subscribe_warning", () => {
 
 test_ui("warn_if_private_stream_is_linked", ({mock_template}) => {
     const $textarea = $("<textarea>").attr("id", "compose-textarea");
+    stub_message_row($textarea);
     const test_sub = {
         name: compose_state.stream_name(),
         stream_id: 99,
@@ -676,6 +686,7 @@ test_ui("warn_if_private_stream_is_linked", ({mock_template}) => {
 test_ui("warn_if_mentioning_unsubscribed_user", ({override, override_rewire, mock_template}) => {
     override_rewire(compose_recipient, "on_compose_select_recipient_update", () => {});
     const $textarea = $("<textarea>").attr("id", "compose-textarea");
+    stub_message_row($textarea);
     compose_state.set_stream_name("");
     override(settings_data, "user_can_subscribe_other_users", () => true);