diff --git a/Orange/data/sql/backend/mssql.py b/Orange/data/sql/backend/mssql.py
index 6d136043472..051b0d8adf9 100644
--- a/Orange/data/sql/backend/mssql.py
+++ b/Orange/data/sql/backend/mssql.py
@@ -24,6 +24,9 @@ def __init__(self, connection_params):
             self.connection = pymssql.connect(login_timeout=5, **connection_params)
         except pymssql.Error as ex:
             raise BackendError(str(ex)) from ex
+        except ValueError:
+            # ValueError is raised when 'server' contains "\\"
+            raise BackendError("Incorrect format of connection details")
 
     def list_tables_query(self, schema=None):
         return """