diff --git a/src/main/java/envoy/client/ui/controller/LoginScene.java b/src/main/java/envoy/client/ui/controller/LoginScene.java
index b17fa81..5c6fab9 100644
--- a/src/main/java/envoy/client/ui/controller/LoginScene.java
+++ b/src/main/java/envoy/client/ui/controller/LoginScene.java
@@ -23,6 +23,7 @@ import envoy.event.EventBus;
 import envoy.event.HandshakeRejection;
 import envoy.event.MessageStatusChange;
 import envoy.exception.EnvoyException;
+import envoy.util.Bounds;
 import envoy.util.EnvoyLog;
 
 /**
@@ -115,8 +116,11 @@ public final class LoginScene {
 		if (registerCheckBox.isSelected() && !passwordField.getText().equals(repeatPasswordField.getText())) {
 			new Alert(AlertType.ERROR, "The entered password is unequal to the repeated one").showAndWait();
 			repeatPasswordField.clear();
-		}
-		else performHandshake(
+		} else if (!Bounds.isValidContactName(userTextField.getText())) {
+			new Alert(AlertType.ERROR, "The entered user name is not valid (" + Bounds.CONTACT_NAME_PATTERN.toString() + ")").showAndWait();
+			userTextField.clear();
+		} else
+			performHandshake(
 				new LoginCredentials(userTextField.getText(), passwordField.getText().toCharArray(), registerCheckBox.isSelected(), Startup.VERSION));
 	}