diff --git a/frontend_tests/node_tests/drafts.js b/frontend_tests/node_tests/drafts.js
index d44b7bacae..f9e9d9bad7 100644
--- a/frontend_tests/node_tests/drafts.js
+++ b/frontend_tests/node_tests/drafts.js
@@ -413,7 +413,7 @@ test("catch_buggy_draft_error", () => {
     // An error is logged but the draft isn't fixed in this codepath.
     blueslip.expect(
         "error",
-        "Cannot compare strings; at least one value is undefined: undefined, old_topic",
+        "Cannot compare strings; at least one value is undefined: (undefined), old_topic",
     );
     drafts.rename_stream_recipient(
         stream_B.stream_id,
diff --git a/static/js/util.js b/static/js/util.js
index f20aad4bc5..fe5a722d78 100644
--- a/static/js/util.js
+++ b/static/js/util.js
@@ -41,7 +41,10 @@ export function lower_bound(array, value, less) {
 
 export const lower_same = function lower_same(a, b) {
     if (a === undefined || b === undefined) {
-        blueslip.error(`Cannot compare strings; at least one value is undefined: ${a}, ${b}`);
+        blueslip.error(
+            `Cannot compare strings; at least one value is undefined: \
+${a ?? "(undefined)"}, ${b ?? "(undefined)"}`,
+        );
         return false;
     }
     return a.toLowerCase() === b.toLowerCase();