diff --git a/lib/siplib.py b/lib/siplib.py
index 2c9a9f46b26927aab6fd8f51d395d8367c2d2147..a4f9faf5867c93e730a709c2328d8a7f71487188 100644
--- a/lib/siplib.py
+++ b/lib/siplib.py
@@ -41,6 +41,14 @@ logger = logging.getLogger(__name__)
 VERSION = "SIPlib 0.4"
 ltasip.Namespace.setPrefix('sip')
 
+# The LTA catalogue expectes all lofar complexType objects to be annotated as xsi:type="<my_type>"
+# Trick pyxb into doing this, by override the _RequireXSIType, and make the xsitype required for out types.
+import inspect
+from pyxb.binding.basis import complexTypeDefinition
+for member in inspect.getmembers(ltasip, inspect.isclass):
+    if issubclass(member[1], complexTypeDefinition):
+        member[1]._RequireXSIType = classmethod(lambda _1, _2: True)
+
 # todo: create docstrings for everything.
 # specify types and explain purpose of the field (-> ask someone with more astronomical background)