diff --git a/.eslintrc.json b/.eslintrc.json
index 96be4766ab..fde02677a9 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -348,6 +348,7 @@
                 "document": false,
                 "set_global": false,
                 "window": false,
+                "with_field": false,
                 "zrequire": false
             },
             "rules": {
diff --git a/frontend_tests/node_tests/markdown.js b/frontend_tests/node_tests/markdown.js
index 5d0dc97e6a..e1daff6765 100644
--- a/frontend_tests/node_tests/markdown.js
+++ b/frontend_tests/node_tests/markdown.js
@@ -758,12 +758,9 @@ run_test("missing unicode emojis", () => {
         // return undefined
     }
 
-    const actual_get_emoji_name = emoji.get_emoji_name;
-    emoji.get_emoji_name = fake_get_emoji_name;
+    with_field(emoji, "get_emoji_name", fake_get_emoji_name, () => {
+        markdown.apply_markdown(message);
+    });
 
-    markdown.apply_markdown(message);
     assert.equal(message.content, "<p>\u{1f6b2}</p>");
-
-    // restore get_emoji_name for any future tests that follow
-    emoji.get_emoji_name = actual_get_emoji_name;
 });
diff --git a/frontend_tests/zjsunit/index.js b/frontend_tests/zjsunit/index.js
index 1aa5193ab8..1fa70d006a 100644
--- a/frontend_tests/zjsunit/index.js
+++ b/frontend_tests/zjsunit/index.js
@@ -37,6 +37,7 @@ if (files.length === 0) {
 }
 
 // Set up our namespace helpers.
+global.with_field = namespace.with_field;
 global.set_global = namespace.set_global;
 global.patch_builtin = namespace.set_global;
 global.zrequire = namespace.zrequire;
diff --git a/frontend_tests/zjsunit/namespace.js b/frontend_tests/zjsunit/namespace.js
index be767e1048..effe06e6c3 100644
--- a/frontend_tests/zjsunit/namespace.js
+++ b/frontend_tests/zjsunit/namespace.js
@@ -69,6 +69,13 @@ exports.stub_out_jquery = function () {
     $.now = function () {};
 };
 
+exports.with_field = function (obj, field, val, f) {
+    const old_val = obj[field];
+    obj[field] = val;
+    f();
+    obj[field] = old_val;
+};
+
 exports.with_overrides = function (test_function) {
     // This function calls test_function() and passes in
     // a way to override the namespace temporarily.