diff --git a/edit.js b/edit.js
index a2043067..7fc06efd 100644
--- a/edit.js
+++ b/edit.js
@@ -1551,8 +1551,8 @@ function showKeyMapHelp() {
 			cell.innerHTML = cell.textContent;
 		});
 	}
-	function mergeKeyMaps(merged) {
-		[].slice.call(arguments, 1).forEach(function(keyMap) {
+	function mergeKeyMaps(merged, ...more) {
+		more.forEach(keyMap => {
 			if (typeof keyMap == "string") {
 				keyMap = CodeMirror.keyMap[keyMap];
 			}
diff --git a/messaging.js b/messaging.js
index ba3aba52..f8173814 100644
--- a/messaging.js
+++ b/messaging.js
@@ -183,7 +183,10 @@ function wildcardAsRegExp(s, flags) {
 }
 
 
-var configureCommands = {
+// isolate deoptimization trigger:
+// https://github.com/petkaantonov/bluebird/wiki/Optimization-killers
+// * Functions that contain object literals that contain __proto__, or get or set declarations.
+const configureCommands = (() => ({
 	get url () {
 		return navigator.userAgent.indexOf('OPR') > -1 ?
 			'opera://settings/configureCommands' :
@@ -194,4 +197,4 @@ var configureCommands = {
 			'url': configureCommands.url
 		});
 	}
-};
+}))();