--- a/browser/locales/en-US/chrome/browser/browser.properties
+++ b/browser/locales/en-US/chrome/browser/browser.properties
@@ -56,22 +56,22 @@ webextPerms.cancel.accessKey=C
 webextPerms.sideloadMenuItem=%1$S added to %2$S
 
 # LOCALIZATION NOTE (webextPerms.sideloadHeader)
 # This string is used as a header in the webextension permissions dialog
 # when the extension is side-loaded.
 # %S is replaced with the localized name of the extension being installed.
 # Note, this string will be used as raw markup. Avoid characters like <, >, &
 webextPerms.sideloadHeader=%S added
-webextPerms.sideloadText=Another program on your computer installed an add-on that may affect your browser. Please review this add-on’s permissions requests and choose to Enable or Disable.
+webextPerms.sideloadText2=Another program on your computer installed an add-on that may affect your browser. Please review this add-on’s permissions requests and choose to Enable or Cancel (to leave it disabled).
 
 webextPerms.sideloadEnable.label=Enable
 webextPerms.sideloadEnable.accessKey=E
-webextPerms.sideloadDisable.label=Disable
-webextPerms.sideloadDisable.accessKey=D
+webextPerms.sideloadCancel.label=Cancel
+webextPerms.sideloadCancel.accessKey=C
 
 # LOCALIZATION NOTE (webextPerms.updateMenuItem)
 # %S will be replaced with the localized name of the extension which
 # has been updated.
 webextPerms.updateMenuItem=%S requires new permissions
 
 # LOCALIZATION NOTE (webextPerms.updateText)
 # %S is replaced with the localized name of the updated extension.

--- a/browser/modules/ExtensionsUI.jsm
+++ b/browser/modules/ExtensionsUI.jsm
@@ -190,21 +190,21 @@ this.ExtensionsUI = {
 
     result.acceptText = bundle.GetStringFromName("webextPerms.add.label");
     result.acceptKey = bundle.GetStringFromName("webextPerms.add.accessKey");
     result.cancelText = bundle.GetStringFromName("webextPerms.cancel.label");
     result.cancelKey = bundle.GetStringFromName("webextPerms.cancel.accessKey");
 
     if (info.type == "sideload") {
       result.header = bundle.formatStringFromName("webextPerms.sideloadHeader", [addonName], 1);
-      result.text = bundle.GetStringFromName("webextPerms.sideloadText");
+      result.text = bundle.GetStringFromName("webextPerms.sideloadText2");
       result.acceptText = bundle.GetStringFromName("webextPerms.sideloadEnable.label");
       result.acceptKey = bundle.GetStringFromName("webextPerms.sideloadEnable.accessKey");
-      result.cancelText = bundle.GetStringFromName("webextPerms.sideloadDisable.label");
-      result.cancelKey = bundle.GetStringFromName("webextPerms.sideloadDisable.accessKey");
+      result.cancelText = bundle.GetStringFromName("webextPerms.sideloadCancel.label");
+      result.cancelKey = bundle.GetStringFromName("webextPerms.sideloadCancel.accessKey");
     } else if (info.type == "update") {
       result.header = "";
       result.text = bundle.formatStringFromName("webextPerms.updateText", [addonName], 1);
       result.acceptText = bundle.GetStringFromName("webextPerms.updateAccept.label");
       result.acceptKey = bundle.GetStringFromName("webextPerms.updateAccept.accessKey");
     }
 
     let perms = info.permissions || {hosts: [], permissions: []};