diff --git a/src/main/java/eu/siacs/conversations/services/XmppConnectionService.java b/src/main/java/eu/siacs/conversations/services/XmppConnectionService.java
index 6f342691c..66bb4136e 100644
--- a/src/main/java/eu/siacs/conversations/services/XmppConnectionService.java
+++ b/src/main/java/eu/siacs/conversations/services/XmppConnectionService.java
@@ -2348,9 +2348,12 @@ public class XmppConnectionService extends Service {
 		return false;
 	}
 
-	public void renameInMuc(final Conversation conversation, final String nick, final UiCallback<Conversation> callback) {
+	public boolean renameInMuc(final Conversation conversation, final String nick, final UiCallback<Conversation> callback) {
 		final MucOptions options = conversation.getMucOptions();
 		final Jid joinJid = options.createJoinJid(nick);
+		if (joinJid == null) {
+			return false;
+		}
 		if (options.online()) {
 			Account account = conversation.getAccount();
 			options.setOnRenameListener(new OnRenameListener() {
@@ -2395,6 +2398,7 @@ public class XmppConnectionService extends Service {
 				joinMuc(conversation);
 			}
 		}
+		return true;
 	}
 
 	public void leaveMuc(Conversation conversation) {
diff --git a/src/main/java/eu/siacs/conversations/ui/ConferenceDetailsActivity.java b/src/main/java/eu/siacs/conversations/ui/ConferenceDetailsActivity.java
index 294db3ee5..d019834f3 100644
--- a/src/main/java/eu/siacs/conversations/ui/ConferenceDetailsActivity.java
+++ b/src/main/java/eu/siacs/conversations/ui/ConferenceDetailsActivity.java
@@ -204,8 +204,9 @@ public class ConferenceDetailsActivity extends XmppActivity implements OnConvers
 	private OnValueEdited onSubjectEdited = new OnValueEdited() {
 
 		@Override
-		public void onValueEdited(String value) {
+		public String onValueEdited(String value) {
 			xmppConnectionService.pushSubjectToConference(mConversation,value);
+			return null;
 		}
 	};
 
@@ -254,8 +255,12 @@ public class ConferenceDetailsActivity extends XmppActivity implements OnConvers
 						new OnValueEdited() {
 
 							@Override
-							public void onValueEdited(String value) {
-								xmppConnectionService.renameInMuc(mConversation,value,renameCallback);
+							public String onValueEdited(String value) {
+								if (xmppConnectionService.renameInMuc(mConversation,value,renameCallback)) {
+									return null;
+								} else {
+									return getString(R.string.invalid_username);
+								}
 							}
 						});
 			}
diff --git a/src/main/java/eu/siacs/conversations/ui/ContactDetailsActivity.java b/src/main/java/eu/siacs/conversations/ui/ContactDetailsActivity.java
index 3de3c4df2..48107a4ab 100644
--- a/src/main/java/eu/siacs/conversations/ui/ContactDetailsActivity.java
+++ b/src/main/java/eu/siacs/conversations/ui/ContactDetailsActivity.java
@@ -284,11 +284,11 @@ public class ContactDetailsActivity extends OmemoActivity implements OnAccountUp
 					quickEdit(contact.getDisplayName(), 0, new OnValueEdited() {
 
 						@Override
-						public void onValueEdited(String value) {
+						public String onValueEdited(String value) {
 							contact.setServerName(value);
-							ContactDetailsActivity.this.xmppConnectionService
-								.pushContactToServer(contact);
+							ContactDetailsActivity.this.xmppConnectionService.pushContactToServer(contact);
 							populateView();
+							return null;
 						}
 					});
 				} else {
diff --git a/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java b/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
index 897bd7cbc..9bd90902f 100644
--- a/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
+++ b/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
@@ -133,9 +133,9 @@ public class ConversationFragment extends Fragment implements EditMessage.Keyboa
 			activity.quickPasswordEdit(password, new OnValueEdited() {
 
 				@Override
-				public void onValueEdited(String value) {
-					activity.xmppConnectionService.providePasswordForMuc(
-							conversation, value);
+				public String onValueEdited(String value) {
+					activity.xmppConnectionService.providePasswordForMuc(conversation, value);
+					return null;
 				}
 			});
 		}
diff --git a/src/main/java/eu/siacs/conversations/ui/XmppActivity.java b/src/main/java/eu/siacs/conversations/ui/XmppActivity.java
index 8bf84af0c..a531fe8cf 100644
--- a/src/main/java/eu/siacs/conversations/ui/XmppActivity.java
+++ b/src/main/java/eu/siacs/conversations/ui/XmppActivity.java
@@ -7,6 +7,7 @@ import android.app.ActionBar;
 import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.AlertDialog.Builder;
+import android.app.Dialog;
 import android.app.PendingIntent;
 import android.content.ActivityNotFoundException;
 import android.content.ClipData;
@@ -167,11 +168,11 @@ public abstract class XmppActivity extends Activity {
 	abstract protected void refreshUiReal();
 
 	protected interface OnValueEdited {
-		public void onValueEdited(String value);
+		String onValueEdited(String value);
 	}
 
 	public interface OnPresenceSelected {
-		public void onPresenceSelected();
+		void onPresenceSelected();
 	}
 
 	protected ServiceConnection mConnection = new ServiceConnection() {
@@ -733,23 +734,13 @@ public abstract class XmppActivity extends Activity {
 						   boolean password) {
 		AlertDialog.Builder builder = new AlertDialog.Builder(this);
 		View view = getLayoutInflater().inflate(R.layout.quickedit, null);
-		final EditText editor = (EditText) view.findViewById(R.id.editor);
-		OnClickListener mClickListener = new OnClickListener() {
-
-			@Override
-			public void onClick(DialogInterface dialog, int which) {
-				String value = editor.getText().toString();
-				if (!value.equals(previousValue) && value.trim().length() > 0) {
-					callback.onValueEdited(value);
-				}
-			}
-		};
+		final EditText editor = view.findViewById(R.id.editor);
 		if (password) {
 			editor.setInputType(InputType.TYPE_CLASS_TEXT
 					| InputType.TYPE_TEXT_VARIATION_PASSWORD);
-			builder.setPositiveButton(R.string.accept, mClickListener);
+			builder.setPositiveButton(R.string.accept,null);
 		} else {
-			builder.setPositiveButton(R.string.edit, mClickListener);
+			builder.setPositiveButton(R.string.edit, null);
 		}
 		if (hint != 0) {
 			editor.setHint(hint);
@@ -761,7 +752,24 @@ public abstract class XmppActivity extends Activity {
 		}
 		builder.setView(view);
 		builder.setNegativeButton(R.string.cancel, null);
-		builder.create().show();
+		final AlertDialog dialog = builder.create();
+		dialog.show();
+		View.OnClickListener clickListener = new View.OnClickListener() {
+
+			@Override
+			public void onClick(View v) {
+				String value = editor.getText().toString();
+				if (!value.equals(previousValue) && value.trim().length() > 0) {
+					String error = callback.onValueEdited(value);
+					if (error != null) {
+						editor.setError(error);
+						return;
+					}
+				}
+				dialog.dismiss();
+			}
+		};
+		dialog.getButton(DialogInterface.BUTTON_POSITIVE).setOnClickListener(clickListener);
 	}
 
 	public boolean hasStoragePermission(int requestCode) {