diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index e9e3f1a3a..6040a50d6 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -60,10 +60,11 @@
                 android:name="android.app.default_searchable"
                 android:value=".SearchResults" />
         </activity>
-
         <activity
             android:name=".ManageRepo"
+            android:allowTaskReparenting="true"
             android:label="@string/menu_manage"
+            android:launchMode="singleTop"
             android:parentActivityName=".FDroid" >
             <meta-data
                 android:name="android.support.PARENT_ACTIVITY"
@@ -99,7 +100,7 @@
                 <data android:pathPattern="/.*/.*/fdroid/archive/*" />
                 <data android:pathPattern="/.*/.*/.*/fdroid/archive" />
                 <data android:pathPattern="/.*/.*/.*/fdroid/archive/*" />
-                </intent-filter>
+            </intent-filter>
             <intent-filter>
                 <action android:name="android.intent.action.VIEW" />
 
diff --git a/res/layout/addrepo.xml b/res/layout/addrepo.xml
index 95882888e..0638049ee 100644
--- a/res/layout/addrepo.xml
+++ b/res/layout/addrepo.xml
@@ -4,17 +4,6 @@
     android:layout_height="wrap_content"
     android:orientation="vertical" >
 
-    <TextView
-        android:id="@+id/repo_alert"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:drawableLeft="@android:drawable/ic_dialog_alert"
-        android:gravity="center"
-        android:text="@string/repo_exists"
-        android:textAppearance="@android:style/TextAppearance.Large"
-        android:textColor="@color/red"
-        android:visibility="gone" />
-
     <TextView
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
@@ -25,7 +14,7 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:inputType="textUri"
-        android:maxLines="1"
+        android:maxLines="2"
         android:text="https://" />
 
     <TextView
@@ -39,15 +28,17 @@
         android:layout_height="wrap_content"
         android:digits="0123456789ABCDEFabcedf: "
         android:inputType="textNoSuggestions"
-        android:maxLines="1"
+        android:maxLines="3"
         android:typeface="monospace" />
 
-    <CheckBox
-        android:id="@+id/overwrite_repo"
+    <TextView
+        android:id="@+id/overwrite_message"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
+        android:drawableLeft="@android:drawable/ic_dialog_alert"
+        android:drawablePadding="20dp"
         android:padding="20dp"
-        android:text="@string/repo_overwrite"
+        android:text="@string/repo_delete_to_overwrite"
         android:textAppearance="@android:style/TextAppearance.Medium"
         android:visibility="gone" />
 
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 58f105812..1093ddcd3 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -56,6 +56,9 @@
 	<string name="repo_add_add">Add</string>
 
 	<string name="cancel">Cancel</string>
+	<string name="enable">Enable</string>
+	<string name="add_key">Add Key</string>
+	<string name="overwrite">Overwrite</string>
 	<string name="repo_delete_title">Choose repository to remove</string>
 
 	<string name="repo_update_title">Update repositories</string>
@@ -72,7 +75,10 @@
 	<string name="repo_add_url">Repository address</string>
 	<string name="repo_add_fingerprint">fingerprint (optional)</string>
 	<string name="repo_exists">This repo already exists!</string>
-	<string name="repo_overwrite">Overwrite the existing repo?</string>
+	<string name="repo_exists_add_fingerprint">This repo is already setup, this will add new key information.</string>
+	<string name="repo_exists_enable">This repo is already setup, confirm that you want to re-enable it.</string>
+	<string name="repo_exists_and_enabled">The incoming repo is already setup and enabled!</string>
+	<string name="repo_delete_to_overwrite">You must first delete this repo before you can add one with a different key!</string>
 
 	<string name="repo_alrt">The list of used repositories has
 		changed.\nDo you
diff --git a/src/org/fdroid/fdroid/DB.java b/src/org/fdroid/fdroid/DB.java
index ef950ef69..73236124e 100644
--- a/src/org/fdroid/fdroid/DB.java
+++ b/src/org/fdroid/fdroid/DB.java
@@ -11,7 +11,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
@@ -465,6 +465,8 @@ public class DB {
 
     public static String calcFingerprint(String pubkey) {
         String ret = null;
+        if (pubkey == null)
+            return null;
         try {
             // keytool -list -v gives you the SHA-256 fingerprint
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
@@ -1410,7 +1412,7 @@ public class DB {
         String calcedFingerprint = DB.calcFingerprint(pubkey);
         if (fingerprint == null) {
             fingerprint = calcedFingerprint;
-        } else {
+        } else if (calcedFingerprint != null) {
             fingerprint = fingerprint.toUpperCase();
             if (!fingerprint.equals(calcedFingerprint)) {
                 throw new SecurityException("Given fingerprint does not match calculated one! ("
diff --git a/src/org/fdroid/fdroid/FDroid.java b/src/org/fdroid/fdroid/FDroid.java
index 63353ffec..e78135ef9 100644
--- a/src/org/fdroid/fdroid/FDroid.java
+++ b/src/org/fdroid/fdroid/FDroid.java
@@ -11,7 +11,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/FDroidApp.java b/src/org/fdroid/fdroid/FDroidApp.java
index b7dea120d..a9cb64ab0 100644
--- a/src/org/fdroid/fdroid/FDroidApp.java
+++ b/src/org/fdroid/fdroid/FDroidApp.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/ManageRepo.java b/src/org/fdroid/fdroid/ManageRepo.java
index 4185e89fc..de5b6c884 100644
--- a/src/org/fdroid/fdroid/ManageRepo.java
+++ b/src/org/fdroid/fdroid/ManageRepo.java
@@ -11,7 +11,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
@@ -26,6 +26,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 
+import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.AlertDialog.Builder;
 import android.app.ListActivity;
@@ -35,24 +36,22 @@ import android.content.SharedPreferences;
 import android.net.Uri;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
+import android.support.v4.app.NavUtils;
+import android.support.v4.view.MenuItemCompat;
 import android.text.format.DateFormat;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
-import android.view.View.OnClickListener;
 import android.widget.Button;
-import android.widget.CheckBox;
 import android.widget.EditText;
 import android.widget.ListView;
 import android.widget.SimpleAdapter;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import org.fdroid.fdroid.DB.Repo;
-import android.support.v4.app.NavUtils;
-import android.support.v4.view.MenuItemCompat;
-
 import org.fdroid.fdroid.compat.ActionBarCompat;
 
 public class ManageRepo extends ListActivity {
@@ -62,6 +61,11 @@ public class ManageRepo extends ListActivity {
 
     private boolean changed = false;
 
+    private enum PositiveAction {
+        ADD_NEW, ENABLE, IGNORE
+    }
+    private PositiveAction positiveAction;
+
     private List<DB.Repo> repos;
 
     private static List<String> reposToDisable;
@@ -103,7 +107,7 @@ public class ManageRepo extends ListActivity {
             s_lastUpdateCheck = getString(R.string.never);
         } else {
             Date d = new Date(lastUpdate);
-            s_lastUpdateCheck = DateFormat.getDateFormat(this).format(d) + 
+            s_lastUpdateCheck = DateFormat.getDateFormat(this).format(d) +
                     " " + DateFormat.getTimeFormat(this).format(d);
         }
         tv_lastCheck.setText(getString(R.string.last_update_check,s_lastUpdateCheck));
@@ -116,13 +120,25 @@ public class ManageRepo extends ListActivity {
         /* an URL from a click or a QRCode scan */
         Uri uri = intent.getData();
         if (uri != null) {
-            // scheme should only ever be pure ASCII:
+            // scheme should only ever be pure ASCII aka Locale.ENGLISH
             String scheme = intent.getScheme().toLowerCase(Locale.ENGLISH);
             String fingerprint = uri.getUserInfo();
+            String host = uri.getHost().toLowerCase(Locale.ENGLISH);
             if (scheme.equals("fdroidrepos") || scheme.equals("fdroidrepo")
                     || scheme.equals("https") || scheme.equals("http")) {
-                String uriString = uri.toString().replace("fdroidrepo", "http").
-                        replace(fingerprint + "@", "");
+                // QRCode are more efficient in all upper case, so some incoming
+                // URLs might be encoded in all upper case. Therefore, we allow
+                // the standard paths to be encoded all upper case, then they'll
+                // be forced to lower case. The scheme and host are downcased
+                // just to make them more readable in the dialog.
+                String uriString = uri.toString()
+                        .replace(fingerprint + "@", "") // remove fingerprint
+                        .replaceAll("/*$", "") // remove all trailing slashes
+                        .replaceAll("/FDROID/REPO$", "/fdroid/repo")
+                        .replaceAll("/FDROID/ARCHIVE$", "/fdroid/archive")
+                        .replace(uri.getHost(), host) // downcase host name
+                        .replace(intent.getScheme(), scheme) // downcase scheme
+                        .replace("fdroidrepo", "http"); // make proper URL
                 showAddRepo(uriString, fingerprint);
                 Log.i("ManageRepo", uriString + " fingerprint: " + fingerprint);
             }
@@ -219,10 +235,10 @@ public class ManageRepo extends ListActivity {
         return repos;
     }
 
-    protected Repo getRepo(String repoUri, List<Repo> repos) {
-        if (repoUri != null)
+    protected Repo getRepoByAddress(String address, List<Repo> repos) {
+        if (address != null)
             for (Repo repo : repos)
-                if (repoUri.equals(repo.address))
+                if (address.equals(repo.address))
                     return repo;
         return null;
     }
@@ -237,7 +253,7 @@ public class ManageRepo extends ListActivity {
         return super.onOptionsItemSelected(item);
     }
 
-    private void showAddRepo(String uriString, String fingerprint) {
+    private void showAddRepo(String newAddress, String newFingerprint) {
         LayoutInflater li = LayoutInflater.from(this);
         View view = li.inflate(R.layout.addrepo, null);
         Builder p = new AlertDialog.Builder(this).setView(view);
@@ -245,6 +261,9 @@ public class ManageRepo extends ListActivity {
         final EditText uriEditText = (EditText) view.findViewById(R.id.edit_uri);
         final EditText fingerprintEditText = (EditText) view.findViewById(R.id.edit_fingerprint);
 
+        List<Repo> repos = getRepos();
+        final Repo repo = getRepoByAddress(newAddress, repos);
+
         alrt.setIcon(android.R.drawable.ic_menu_add);
         alrt.setTitle(getString(R.string.repo_add_title));
         alrt.setButton(DialogInterface.BUTTON_POSITIVE,
@@ -252,10 +271,15 @@ public class ManageRepo extends ListActivity {
                 new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {
-                        addRepo(uriEditText.getText().toString(),
-                                fingerprintEditText.getText().toString());
-                        changed = true;
-                        redraw();
+                        String fp = fingerprintEditText.getText().toString();
+                        // the DB uses null for no fingerprint but the above
+                        // code returns "" rather than null if its blank
+                        if (fp.equals(""))
+                            fp = null;
+                        if (positiveAction == PositiveAction.ADD_NEW)
+                            addRepoPositiveAction(uriEditText.getText().toString(), fp, null);
+                        else if (positiveAction == PositiveAction.ENABLE)
+                            addRepoPositiveAction(null, null, repo);
                     }
                 });
 
@@ -264,35 +288,74 @@ public class ManageRepo extends ListActivity {
                 new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {
+                        setResult(Activity.RESULT_CANCELED);
+                        finish();
                         return;
                     }
                 });
         alrt.show();
 
-        List<Repo> repos = getRepos();
-        Repo repo = getRepo(uriString, repos);
-        if (repo != null) {
-            TextView tv = (TextView) view.findViewById(R.id.repo_alert);
-            tv.setVisibility(0);
-            tv.setText(R.string.repo_exists);
+        final TextView overwriteMessage = (TextView) view.findViewById(R.id.overwrite_message);
+        overwriteMessage.setVisibility(View.GONE);
+        if (repo == null) {
+            // no existing repo, add based on what we have
+            positiveAction = PositiveAction.ADD_NEW;
+        } else {
+            // found the address in the DB of existing repos
             final Button addButton = alrt.getButton(DialogInterface.BUTTON_POSITIVE);
-            addButton.setEnabled(false);
-            final CheckBox overwriteCheckBox = (CheckBox) view.findViewById(R.id.overwrite_repo);
-            overwriteCheckBox.setVisibility(0);
-            overwriteCheckBox.setOnClickListener(new OnClickListener() {
-                @Override
-                public void onClick(View v) {
-                    addButton.setEnabled(overwriteCheckBox.isChecked());
+            alrt.setTitle(R.string.repo_exists);
+            overwriteMessage.setVisibility(View.VISIBLE);
+            if (repo.fingerprint == null && newFingerprint != null) {
+                // we're upgrading from unsigned to signed repo
+                overwriteMessage.setText(R.string.repo_exists_add_fingerprint);
+                addButton.setText(R.string.add_key);
+                positiveAction = PositiveAction.ADD_NEW;
+            } else if (newFingerprint == null || newFingerprint.equals(repo.fingerprint)) {
+                // this entry already exists and is not enabled, offer to enable it
+                if (repo.inuse) {
+                    alrt.dismiss();
+                    Toast.makeText(this, R.string.repo_exists_and_enabled, Toast.LENGTH_LONG).show();
+                    return;
+                } else {
+                    overwriteMessage.setText(R.string.repo_exists_enable);
+                    addButton.setText(R.string.enable);
+                    positiveAction = PositiveAction.ENABLE;
                 }
-            });
-            // TODO if address and fingerprint match, then enable existing repo
-            // TODO if address matches but fingerprint doesn't, handle this with extra widgets
+            } else {
+                // same address with different fingerprint, this could be
+                // malicious, so force the user to manually delete the repo
+                // before adding this one
+                overwriteMessage.setTextColor(getResources().getColor(R.color.red));
+                overwriteMessage.setText(R.string.repo_delete_to_overwrite);
+                addButton.setText(R.string.overwrite);
+                addButton.setEnabled(false);
+                positiveAction = PositiveAction.IGNORE;
+            }
         }
 
-        if (uriString != null)
-            uriEditText.setText(uriString);
-        if (fingerprint != null)
-            fingerprintEditText.setText(fingerprint);
+        if (newAddress != null)
+            uriEditText.setText(newAddress);
+        if (newFingerprint != null)
+            fingerprintEditText.setText(newFingerprint);
+    }
+
+    private void addRepoPositiveAction(String address, String fingerprint, Repo repo) {
+        if (address != null) {
+            addRepo(address, fingerprint);
+        } else if (repo != null) {
+            // force-enable an existing repo
+            repo.inuse = true;
+            try {
+                DB db = DB.getDB();
+                db.updateRepoByAddress(repo);
+            } finally {
+                DB.releaseDB();
+            }
+        }
+        changed = true;
+        redraw();
+        setResult(Activity.RESULT_OK);
+        finish();
     }
 
     @Override
diff --git a/src/org/fdroid/fdroid/PackageReceiver.java b/src/org/fdroid/fdroid/PackageReceiver.java
index 5716c5dc7..180aa3f8c 100644
--- a/src/org/fdroid/fdroid/PackageReceiver.java
+++ b/src/org/fdroid/fdroid/PackageReceiver.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/PreferencesActivity.java b/src/org/fdroid/fdroid/PreferencesActivity.java
index d0690d808..1303e9f09 100644
--- a/src/org/fdroid/fdroid/PreferencesActivity.java
+++ b/src/org/fdroid/fdroid/PreferencesActivity.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/RepoXMLHandler.java b/src/org/fdroid/fdroid/RepoXMLHandler.java
index 8af50821f..29648f7c9 100644
--- a/src/org/fdroid/fdroid/RepoXMLHandler.java
+++ b/src/org/fdroid/fdroid/RepoXMLHandler.java
@@ -11,7 +11,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
@@ -359,7 +359,7 @@ public class RepoXMLHandler extends DefaultHandler {
 
                 // This is a signed repo - we download the jar file,
                 // check the signature, and extract the index...
-                Log.d("FDroid", "Getting signed index from " + repo.address + " at " + 
+                Log.d("FDroid", "Getting signed index from " + repo.address + " at " +
                     logDateFormat.format(new Date(System.currentTimeMillis())));
                 String address = repo.address + "/index.jar?"
                     + ctx.getString(R.string.version_name);
diff --git a/src/org/fdroid/fdroid/SearchResults.java b/src/org/fdroid/fdroid/SearchResults.java
index e1b2ece03..e8afcb002 100644
--- a/src/org/fdroid/fdroid/SearchResults.java
+++ b/src/org/fdroid/fdroid/SearchResults.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/StartupReceiver.java b/src/org/fdroid/fdroid/StartupReceiver.java
index db82be4ca..2d04342dd 100644
--- a/src/org/fdroid/fdroid/StartupReceiver.java
+++ b/src/org/fdroid/fdroid/StartupReceiver.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/src/org/fdroid/fdroid/UpdateService.java b/src/org/fdroid/fdroid/UpdateService.java
index 5323d0e60..c9854f331 100644
--- a/src/org/fdroid/fdroid/UpdateService.java
+++ b/src/org/fdroid/fdroid/UpdateService.java
@@ -10,7 +10,7 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.