diff --git a/src/org/fdroid/fdroid/FDroidCertPins.java b/src/org/fdroid/fdroid/FDroidCertPins.java
index d91563edb..ee5192602 100644
--- a/src/org/fdroid/fdroid/FDroidCertPins.java
+++ b/src/org/fdroid/fdroid/FDroidCertPins.java
@@ -28,6 +28,9 @@ public class FDroidCertPins {
             // Fingerprint: 84B91CDF2312CB9BA7F3BE803783302F8D8C299F
             "638F93856E1F5EDFCBD40C46D4160CFF21B0713A",
 
+            // OU=PositiveSSL, CN=f-droid.org
+            "83a288fdbf7fb27ca2268d553168eb8f38298910",
+
             // OU=Gandi Standard SSL, CN=guardianproject.info
             "cf2f8e226027599a1a933701418c58ec688a8305",
 
diff --git a/src/org/fdroid/fdroid/views/fragments/PreferenceFragment.java b/src/org/fdroid/fdroid/views/fragments/PreferenceFragment.java
index b029f437a..3595a70b6 100644
--- a/src/org/fdroid/fdroid/views/fragments/PreferenceFragment.java
+++ b/src/org/fdroid/fdroid/views/fragments/PreferenceFragment.java
@@ -140,6 +140,16 @@ public class PreferenceFragment
         } else if (key.equals(Preferences.PREF_EXPERT)) {
             onoffSummary(key, R.string.expert_on,
                 R.string.expert_off);
+            CheckBoxPreference pref = (CheckBoxPreference) findPreference(key);
+            Preference rinst = findPreference(Preferences.PREF_ROOT_INSTALLER);
+            Preference sinst = findPreference(Preferences.PREF_SYSTEM_INSTALLER);
+            if (pref.isChecked()) {
+                rinst.setEnabled(true);
+                sinst.setEnabled(true);
+            } else {
+                rinst.setEnabled(false);
+                sinst.setEnabled(false);
+            }
 
         } else if (key.equals(Preferences.PREF_ROOT_INSTALLER)) {
             onoffSummary(key, R.string.root_installer_on,