diff --git a/base_classes/NXbeam.nxdl.xml b/base_classes/NXbeam.nxdl.xml
index 232a75e46..688b49c55 100644
--- a/base_classes/NXbeam.nxdl.xml
+++ b/base_classes/NXbeam.nxdl.xml
@@ -265,7 +265,7 @@
     <field name="depends_on" minOccurs="0" type="NX_CHAR">
         <doc>
             The NeXus coordinate system defines the Z axis to be along the nominal beam
-            direction. This is the same as the McStas coordinate system (see :ref:Design-CoordinateSystem).
+            direction. This is the same as the McStas coordinate system (see :ref:`Design-CoordinateSystem`).
             However, the additional transformations needed to represent an altered beam
             direction can be provided using this depends_on field that contains the path
             to a NXtransformations group. This could represent redirection of the beam,