diff --git a/src/python/errors.py b/src/python/errors.py
index d83e540c..37c28f9e 100644
--- a/src/python/errors.py
+++ b/src/python/errors.py
@@ -52,6 +52,11 @@ class UserNotFound(Exception):
     user_id: str = field()
 
 
+@dataclass
+class InvalidUserId(Exception):
+    user_id: str = field()
+
+
 @dataclass
 class InvalidUserInContext(Exception):
     user_id: str = field()
diff --git a/src/python/matrix_client.py b/src/python/matrix_client.py
index 2a5f7297..8613cacf 100644
--- a/src/python/matrix_client.py
+++ b/src/python/matrix_client.py
@@ -24,8 +24,8 @@ from nio.crypto import async_generator_from_data
 
 from . import __about__, utils
 from .errors import (
-    BadMimeType, InvalidUserInContext, MatrixError, UneededThumbnail,
-    UserNotFound,
+    BadMimeType, InvalidUserId, InvalidUserInContext, MatrixError,
+    UneededThumbnail, UserNotFound,
 )
 from .html_filter import HTML_FILTER
 from .models.items import (
@@ -479,6 +479,9 @@ class MatrixClient(nio.AsyncClient):
         if invite == self.user_id:
             raise InvalidUserInContext(invite)
 
+        if not re.match(r"^@.+:.+", invite):
+            raise InvalidUserId(invite)
+
         if isinstance(await self.get_profile(invite), nio.ProfileGetError):
             raise UserNotFound(invite)
 
diff --git a/src/qml/Pages/AddChat/FindSomeone.qml b/src/qml/Pages/AddChat/FindSomeone.qml
index 0b0074fa..469ed38e 100644
--- a/src/qml/Pages/AddChat/FindSomeone.qml
+++ b/src/qml/Pages/AddChat/FindSomeone.qml
@@ -35,6 +35,10 @@ HBox {
                 if (type === "InvalidUserInContext")
                     txt = qsTr("You can't invite yourself!")
 
+                if (type === "InvalidUserId")
+                    txt = qsTr("Invalid user ID, expected format is " +
+                               "@username:homeserver")
+
                 if (type === "UserNotFound")
                     txt = qsTr("This user does not exist")
 
@@ -61,7 +65,7 @@ HBox {
 
     HTextField {
         id: userField
-        placeholderText: qsTr("User ID (e.g. @john:matrix.org)")
+        placeholderText: qsTr("User ID (e.g. @bob:matrix.org)")
         error: Boolean(errorMessage.text)
 
         Layout.fillWidth: true