diff --git a/core/shortcut_registry.ts b/core/shortcut_registry.ts
index 795a57c73..7bb7f035e 100644
--- a/core/shortcut_registry.ts
+++ b/core/shortcut_registry.ts
@@ -299,9 +299,8 @@ export class ShortcutRegistry {
    * @throws {Error} if the modifier is not in the valid modifiers list.
    */
   private checkModifiers_(modifiers: KeyCodes[]) {
-    const validModifiers = object.values(ShortcutRegistry.modifierKeys);
     for (let i = 0, modifier; modifier = modifiers[i]; i++) {
-      if (validModifiers.indexOf(modifier) < 0) {
+      if (!(modifier in ShortcutRegistry.modifierKeys)) {
         throw new Error(modifier + ' is not a valid modifier key.');
       }
     }
diff --git a/core/utils/deprecation.ts b/core/utils/deprecation.ts
index 5c4b959f6..af2800fb3 100644
--- a/core/utils/deprecation.ts
+++ b/core/utils/deprecation.ts
@@ -18,10 +18,10 @@ goog.declareModuleId('Blockly.utils.deprecation');
  * Warn developers that a function or property is deprecated.
  *
  * @param name The name of the function or property.
- * @param deprecationDate The date of deprecation.
- *     Prefer 'month yyyy' or 'quarter yyyy' format.
- * @param deletionDate The date of deletion, in the same format as the
- *     deprecation date.
+ * @param deprecationDate The date of deprecation. Prefer 'version n.0.0'
+ *     format, and fall back to 'month yyyy' or 'quarter yyyy' format.
+ * @param deletionDate The date of deletion. Prefer 'version n.0.0'
+ *     format, and fall back to 'month yyyy' or 'quarter yyyy' format.
  * @param opt_use The name of a function or property to use instead, if any.
  * @alias Blockly.utils.deprecation.warn
  * @internal
@@ -29,8 +29,8 @@ goog.declareModuleId('Blockly.utils.deprecation');
 export function warn(
     name: string, deprecationDate: string, deletionDate: string,
     opt_use?: string) {
-  let msg = name + ' was deprecated on ' + deprecationDate +
-      ' and will be deleted on ' + deletionDate + '.';
+  let msg = name + ' was deprecated in ' + deprecationDate +
+      ' and will be deleted in ' + deletionDate + '.';
   if (opt_use) {
     msg += '\nUse ' + opt_use + ' instead.';
   }
diff --git a/core/utils/object.ts b/core/utils/object.ts
index 42cb59c22..e094ec612 100644
--- a/core/utils/object.ts
+++ b/core/utils/object.ts
@@ -24,6 +24,8 @@ import * as deprecation from './deprecation.js';
  * @alias Blockly.utils.object.inherits
  */
 export function inherits(childCtor: Function, parentCtor: Function) {
+  deprecation.warn(
+      'Blockly.utils.object.inherits', 'version 9.0.0', 'version 10.0.0');
   // Set a .superClass_ property so that methods can call parent methods
   // without hard-coding the parent class name.
   // Could be replaced by ES6's super().
@@ -86,11 +88,8 @@ export function deepMerge(
  * @alias Blockly.utils.object.values
  */
 export function values(obj: AnyDuringMigration): AnyDuringMigration[] {
-  if (Object.values) {
-    return Object.values(obj);
-  }
-  // Fallback for IE.
-  return Object.keys(obj).map(function(e) {
-    return obj[e];
-  });
+  deprecation.warn(
+      'Blockly.utils.object.values', 'version 9.0.0', 'version 10.0.0',
+      'Object.values');
+  return Object.values(obj);
 }