diff --git a/server/szurubooru/api/user_api.py b/server/szurubooru/api/user_api.py
index 8c70d8e..8bb6ac8 100644
--- a/server/szurubooru/api/user_api.py
+++ b/server/szurubooru/api/user_api.py
@@ -1,8 +1,8 @@
-''' Users public API. '''
+''' Exports UserListApi and UserDetailApi. '''
 
 import sqlalchemy
 from szurubooru.api.base_api import BaseApi
-from szurubooru.errors import IntegrityError, ValidationError
+from szurubooru.errors import IntegrityError, ValidationError, NotFoundError
 from szurubooru.services.search import UserSearchConfig, SearchExecutor
 
 def _serialize_user(authenticated_user, user):
@@ -70,6 +70,8 @@ class UserDetailApi(BaseApi):
         ''' Retrieves an user. '''
         self._auth_service.verify_privilege(context.user, 'users:view')
         user = self._user_service.get_by_name(context.session, user_name)
+        if not user:
+            raise NotFoundError('User %r not found.' % user_name)
         return {'user': _serialize_user(context.user, user)}
 
     def put(self, request, context, user_name):
diff --git a/server/szurubooru/app.py b/server/szurubooru/app.py
index 03b91db..520aaa1 100644
--- a/server/szurubooru/app.py
+++ b/server/szurubooru/app.py
@@ -29,16 +29,21 @@ class _CustomRequest(falcon.Request):
         raise falcon.HTTPMissingParam(name)
 
 def _on_auth_error(ex, request, response, params):
-    raise falcon.HTTPForbidden('Authentication error', str(ex))
+    raise falcon.HTTPForbidden(
+        title='Authentication error', description=str(ex))
 
 def _on_validation_error(ex, request, response, params):
-    raise falcon.HTTPBadRequest('Validation error', str(ex))
+    raise falcon.HTTPBadRequest(title='Validation error', description=str(ex))
 
 def _on_search_error(ex, request, response, params):
-    raise falcon.HTTPBadRequest('Search error', str(ex))
+    raise falcon.HTTPBadRequest(title='Search error', description=str(ex))
 
 def _on_integrity_error(ex, request, response, params):
-    raise falcon.HTTPConflict('Integrity violation', ex.args[0])
+    raise falcon.HTTPConflict(
+        title='Integrity violation', description=ex.args[0])
+
+def _on_not_found_error(ex, request, response, params):
+    raise falcon.HTTPNotFound(title='Not found', description=str(ex))
 
 def create_app():
     ''' Creates a WSGI compatible App object. '''
@@ -78,6 +83,7 @@ def create_app():
     app.add_error_handler(szurubooru.errors.IntegrityError, _on_integrity_error)
     app.add_error_handler(szurubooru.errors.ValidationError, _on_validation_error)
     app.add_error_handler(szurubooru.errors.SearchError, _on_search_error)
+    app.add_error_handler(szurubooru.errors.NotFoundError, _on_not_found_error)
 
     app.add_route('/users/', user_list)
     app.add_route('/user/{user_name}', user)
diff --git a/server/szurubooru/errors.py b/server/szurubooru/errors.py
index f2bec16..fa42ab2 100644
--- a/server/szurubooru/errors.py
+++ b/server/szurubooru/errors.py
@@ -11,3 +11,6 @@ class ValidationError(RuntimeError):
 
 class SearchError(RuntimeError):
     ''' Search error (e.g. trying to use special: where it doesn't make sense) '''
+
+class NotFoundError(RuntimeError):
+    ''' Error thrown when a resource (usually DB) couldn't be found. '''