--- a/netwerk/base/security-prefs.js
+++ b/netwerk/base/security-prefs.js
@@ -35,16 +35,23 @@ pref("security.ssl3.rsa_des_ede3_sha", t
 pref("security.content.signature.root_hash",
      "97:E8:BA:9C:F1:2F:B3:DE:53:CC:42:A4:E6:57:7E:D6:4D:F4:93:C2:47:B4:14:FE:A0:36:81:8D:38:23:56:0E");
 
 pref("security.default_personal_cert",   "Ask Every Time");
 pref("security.remember_cert_checkbox_default_setting", true);
 pref("security.ask_for_password",        0);
 pref("security.password_lifetime",       30);
 
+// The supported values of this pref are:
+// 0: disable detecting Family Safety mode and importing the root
+// 1: only attempt to detect Family Safety mode (don't import the root)
+// 2: detect Family Safety mode and import the root
+// (This is only relevant to Windows 8.1)
+pref("security.family_safety.mode", 2);
+
 pref("security.OCSP.enabled", 1);
 pref("security.OCSP.require", false);
 pref("security.OCSP.GET.enabled", false);
 
 pref("security.pki.cert_short_lifetime_in_days", 10);
 // NB: Changes to this pref affect CERT_CHAIN_SHA1_POLICY_STATUS telemetry.
 // See the comment in CertVerifier.cpp.
 // 3 = allow SHA-1 for certificates issued before 2016 or by an imported root.