diff --git a/zephyr/static/js/hotkey.js b/zephyr/static/js/hotkey.js
index 0f9b8092f0..d74d67f77c 100644
--- a/zephyr/static/js/hotkey.js
+++ b/zephyr/static/js/hotkey.js
@@ -33,7 +33,7 @@ function simulate_keypress(keycode) {
 
 function process_hotkey(code) {
     var next_zephyr, window_to_scroll;
-    if (code in directional_hotkeys) {
+    if (directional_hotkeys.hasOwnProperty(code)) {
         next_zephyr = directional_hotkeys[code](selected_zephyr);
         if (next_zephyr.length !== 0) {
             select_zephyr(next_zephyr, true);
@@ -95,7 +95,7 @@ var goto_hotkeys = {
 };
 
 function process_goto_hotkey(code) {
-    if (code in goto_hotkeys)
+    if (goto_hotkeys.hasOwnProperty(code))
         goto_hotkeys[code]();
 
     /* Always return to the initial hotkey mode, even
diff --git a/zephyr/static/js/zephyr.js b/zephyr/static/js/zephyr.js
index d0c80feddf..0510ccb7be 100644
--- a/zephyr/static/js/zephyr.js
+++ b/zephyr/static/js/zephyr.js
@@ -400,7 +400,7 @@ function add_messages(data) {
 
     // If we received the initially selected message, select it on the client side,
     // but not if the user has already selected another one during load.
-    if ((selected_zephyr_id === -1) && (initial_pointer in zephyr_dict)) {
+    if ((selected_zephyr_id === -1) && (zephyr_dict.hasOwnProperty(initial_pointer))) {
         select_and_show_by_id(initial_pointer);
     }