diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 4e667e7da..c499b50d7 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -393,10 +393,10 @@
                 android:name="android.support.PARENT_ACTIVITY"
                 android:value=".FDroid" />
         </activity>
-        <!-- Note: Theme.NoDisplay, this activity shows dialogs only -->
+        <!-- Note: AppThemeTransparent, this activity shows dialogs only -->
         <activity
             android:name=".privileged.install.InstallExtensionDialogActivity"
-            android:theme="@android:style/Theme.NoDisplay" />
+            android:theme="@style/AppThemeTransparent" />
         <receiver
             android:name=".privileged.install.InstallExtensionBootReceiver" >
             <intent-filter>
diff --git a/app/src/main/java/org/fdroid/fdroid/installer/Installer.java b/app/src/main/java/org/fdroid/fdroid/installer/Installer.java
index a0a549448..cdbb39bc0 100644
--- a/app/src/main/java/org/fdroid/fdroid/installer/Installer.java
+++ b/app/src/main/java/org/fdroid/fdroid/installer/Installer.java
@@ -170,7 +170,7 @@ public abstract class Installer {
      */
     public void installPackage(File apkFile, String packageName, String urlString)
             throws InstallFailedException {
-        SanitizedFile apkToInstall = null;
+        SanitizedFile apkToInstall;
         try {
             Map<String, Object> attributes = AndroidXMLDecompress.getManifestHeaderAttributes(apkFile.getAbsolutePath());
 
diff --git a/app/src/main/java/org/fdroid/fdroid/privileged/install/InstallExtensionDialogActivity.java b/app/src/main/java/org/fdroid/fdroid/privileged/install/InstallExtensionDialogActivity.java
index 221cfb3b5..5305483d2 100644
--- a/app/src/main/java/org/fdroid/fdroid/privileged/install/InstallExtensionDialogActivity.java
+++ b/app/src/main/java/org/fdroid/fdroid/privileged/install/InstallExtensionDialogActivity.java
@@ -206,6 +206,21 @@ public class InstallExtensionDialogActivity extends FragmentActivity {
         // hack to get theme applied (which is not automatically applied due to activity's Theme.NoDisplay
         ContextThemeWrapper theme = new ContextThemeWrapper(this, FDroidApp.getCurThemeResId());
 
+        // not support on Android >= 5.1
+        if (android.os.Build.VERSION.SDK_INT >= 22) {
+            AlertDialog.Builder alertBuilder = new AlertDialog.Builder(theme);
+            alertBuilder.setMessage(R.string.system_install_not_supported);
+            alertBuilder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
+                @Override
+                public void onClick(DialogInterface dialog, int which) {
+                    InstallExtensionDialogActivity.this.setResult(Activity.RESULT_CANCELED);
+                    InstallExtensionDialogActivity.this.finish();
+                }
+            });
+            alertBuilder.create().show();
+            return;
+        }
+
         AlertDialog.Builder alertBuilder = new AlertDialog.Builder(theme);
         alertBuilder.setTitle(R.string.system_install_question);
         String message = InstallExtension.create(getApplicationContext()).getWarningString();
diff --git a/app/src/main/res/values-v23/styles.xml b/app/src/main/res/values-v23/styles.xml
new file mode 100644
index 000000000..628ad2432
--- /dev/null
+++ b/app/src/main/res/values-v23/styles.xml
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <!-- see http://stackoverflow.com/questions/32169303/activity-did-not-call-finish-api-23 -->
+    <style name="AppThemeTransparent" parent="@android:style/Theme.Translucent.NoTitleBar" />
+
+</resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 20d0988a3..d2203a659 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -295,6 +295,7 @@
     <string name="system_install_first_time_message">Looks like you have root access on your device. You can now install F-Droid Privileged Extension, tightly coupled with the Android operating system. This allows F-Droid to install, upgrade and uninstall apps on its own.</string>
     <string name="system_uninstall">Do you want to uninstall F-Droid Privileged Extension?</string>
     <string name="system_uninstall_button">Uninstall</string>
+    <string name="system_install_not_supported">Installation of F-Droid Privileged Extension is currently not supported on Android 5.1 or later.</string>
 
     <string name="swap_nfc_title">Touch to swap</string>
     <string name="swap_nfc_description">If your friend has F-Droid and NFC turned on touch your devices together.</string>
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index 397e2581e..254dbe092 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -237,4 +237,6 @@
     </style>
 
     <style name="AppDetailsSubheaderText" parent="AppDetailsSubheaderTextBase" />
+
+    <style name="AppThemeTransparent" parent="@android:style/Theme.NoDisplay" />
 </resources>