diff --git a/lib/xos-genx/xosgenx/jinja2_extensions/base.py b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
index dd19bd8..1293863 100644
--- a/lib/xos-genx/xosgenx/jinja2_extensions/base.py
+++ b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
@@ -176,7 +176,7 @@
     else:
         return tuple([xproto_tuplify(i) for i in nested_list_or_set])
 
-def xproto_field_graph_components(fields, tag='unique_with'):
+def xproto_field_graph_components(fields, model, tag='unique_with'):
     def find_components(graph):
         pending = set(graph.keys())
         components = []
@@ -188,10 +188,10 @@
             while front:
                 node = front.pop()
                 neighbours = graph[node]
-                neighbours-=component # These we have already visited
+                neighbours -= component  # These we have already visited
                 front |= neighbours
 
-                pending-=neighbours
+                pending -= neighbours
                 component |= neighbours
             
             components.append(component)
@@ -208,15 +208,14 @@
 
             for uf in tagged_fields:
                 if uf not in field_names:
-                    raise FieldNotFound('Field %s not found'%uf)
+                    raise FieldNotFound('Field "%s" not found in model "%s", referenced from field "%s" by option "%s"' % (uf, model['name'], f['name'], tag))
 
-                field_graph.setdefault(f['name'],set()).add(uf)
-                field_graph.setdefault(uf,set()).add(f['name'])
+                field_graph.setdefault(f['name'], set()).add(uf)
+                field_graph.setdefault(uf, set()).add(f['name'])
         except KeyError:
             pass
 
-    components = find_components(field_graph)
-    return components
+    return find_components(field_graph)
 
 def xproto_api_opts(field):
     options = []
diff --git a/lib/xos-genx/xosgenx/jinja2_extensions/tosca.py b/lib/xos-genx/xosgenx/jinja2_extensions/tosca.py
index 9e3b4a8..996d63d 100644
--- a/lib/xos-genx/xosgenx/jinja2_extensions/tosca.py
+++ b/lib/xos-genx/xosgenx/jinja2_extensions/tosca.py
@@ -33,11 +33,11 @@
     else:
         return type
 
-def xproto_fields_to_tosca_keys(fields):
+def xproto_fields_to_tosca_keys(fields, m):
     keys = []
 
     # look for one_of keys
-    _one_of = xproto_field_graph_components(fields, 'tosca_key_one_of')
+    _one_of = xproto_field_graph_components(fields, m, 'tosca_key_one_of')
     one_of = [list(i) for i in _one_of]
 
     # look for explicit keys
diff --git a/lib/xos-genx/xosgenx/targets/django-split.xtarget b/lib/xos-genx/xosgenx/targets/django-split.xtarget
index 60cf9de..200a29f 100644
--- a/lib/xos-genx/xosgenx/targets/django-split.xtarget
+++ b/lib/xos-genx/xosgenx/targets/django-split.xtarget
@@ -38,7 +38,7 @@
   {%- endfor %}
 
   # Meta
-  {%- set uniques = xproto_field_graph_components(m.fields) %}
+  {%- set uniques = xproto_field_graph_components(m.fields, m) %}
   {%- if uniques %}
   class Meta:
       unique_together = {{ xproto_tuplify(uniques) }}
diff --git a/lib/xos-genx/xosgenx/targets/django.xtarget b/lib/xos-genx/xosgenx/targets/django.xtarget
index 13d37f9..631e8cd 100644
--- a/lib/xos-genx/xosgenx/targets/django.xtarget
+++ b/lib/xos-genx/xosgenx/targets/django.xtarget
@@ -76,7 +76,7 @@
 
   # Meta
   class Meta:
-  {%- set uniques = xproto_field_graph_components(m.fields) %}
+  {%- set uniques = xproto_field_graph_components(m.fields, m) %}
   {%- if uniques %}
       unique_together = {{ xproto_tuplify(uniques) }}
   {%- endif %}
diff --git a/lib/xos-genx/xosgenx/targets/service.xtarget b/lib/xos-genx/xosgenx/targets/service.xtarget
index 7b40110..e5816ab 100644
--- a/lib/xos-genx/xosgenx/targets/service.xtarget
+++ b/lib/xos-genx/xosgenx/targets/service.xtarget
@@ -56,7 +56,7 @@
       app_label = {{ xproto_first_non_empty([m.options.app_label, options.app_label, options.name, "Set an app label in your xproto!"]) | lower}}
       # name = {{ xproto_first_non_empty([m.options.name, options.name, "Set a name in your xproto!"]) }}
       verbose_name = "{{ xproto_unquote(xproto_first_non_empty([m.options.verbose_name, m.name])) }}"
-  {%- set uniques = xproto_field_graph_components(m.fields) %}
+  {%- set uniques = xproto_field_graph_components(m.fields, m) %}
   {%- if uniques %}
       unique_together = {{ xproto_tuplify(uniques) }}
   {%- endif %}