diff --git a/web/src/narrow_state.ts b/web/src/narrow_state.ts
index 372d295c82..2145bcdba2 100644
--- a/web/src/narrow_state.ts
+++ b/web/src/narrow_state.ts
@@ -186,6 +186,12 @@ export function pm_ids_string(): string | undefined {
     return user_ids_string;
 }
 
+export function pm_ids_set(): Set<number> {
+    const ids_string = pm_ids_string();
+    const pm_ids_list = ids_string ? people.user_ids_string_to_ids_array(ids_string) : [];
+    return new Set(pm_ids_list);
+}
+
 export function pm_emails_string(): string | undefined {
     if (current_filter === undefined) {
         return undefined;
diff --git a/web/tests/narrow_state.test.js b/web/tests/narrow_state.test.js
index 6e24feb813..d217df6215 100644
--- a/web/tests/narrow_state.test.js
+++ b/web/tests/narrow_state.test.js
@@ -304,18 +304,22 @@ test("pm_ids_string", () => {
     // direct messages) with real users.
     narrow_state.set_current_filter(undefined);
     assert.equal(narrow_state.pm_ids_string(), undefined);
+    assert.deepStrictEqual(narrow_state.pm_ids_set(), new Set());
 
     set_filter([
         ["stream", "Foo"],
         ["topic", "Bar"],
     ]);
     assert.equal(narrow_state.pm_ids_string(), undefined);
+    assert.deepStrictEqual(narrow_state.pm_ids_set(), new Set());
 
     set_filter([["dm", ""]]);
     assert.equal(narrow_state.pm_ids_string(), undefined);
+    assert.deepStrictEqual(narrow_state.pm_ids_set(), new Set());
 
     set_filter([["dm", "bogus@foo.com"]]);
     assert.equal(narrow_state.pm_ids_string(), undefined);
+    assert.deepStrictEqual(narrow_state.pm_ids_set(), new Set());
 
     const alice = {
         email: "alice@foo.com",
@@ -334,4 +338,5 @@ test("pm_ids_string", () => {
 
     set_filter([["dm", "bob@foo.com,alice@foo.com"]]);
     assert.equal(narrow_state.pm_ids_string(), "444,555");
+    assert.deepStrictEqual(narrow_state.pm_ids_set(), new Set([444, 555]));
 });