diff --git a/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_com.py b/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_com.py
index 4a4f72a..9df775c 100644
--- a/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_com.py
+++ b/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_com.py
@@ -25,7 +25,7 @@ def apply(extension_set: Set) -> ABAF:
     rules = abaf_adm_star.rules
     for ext_a, ext_b in aux.tuples(aux.reduce(extension_set).difference(frozenset())):
         for a in aux.unique_big_c(frozenset(set(ext_a).union(set(ext_b))), aux.reduce(extension_set)):
-            x_a_c = 'x_' + a + '_c'
+            x_a_c = 'χ_' + a + '_c'
             rules.add(Rule('', set(ext_a).union(set(ext_b)), x_a_c))
 
     return ABAF(assumptions, rules, language, contraries)
diff --git a/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_ucl.py b/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_ucl.py
index db949ea..ee4725a 100644
--- a/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_ucl.py
+++ b/src/py_arg/algorithms/canonical_constructions/canonical_abaf/canonical_ucl.py
@@ -20,8 +20,8 @@ def apply(extension_set: Set) -> ABAF:
         language.add(a_c)
         contraries[a] = a_c
 
-        x_a = 'x_' + a
-        x_a_c = 'x_' + a + '_c'
+        x_a = 'χ_' + a
+        x_a_c = 'χ_' + a + '_c'
         new_assumptions.add(x_a)
         language.add(x_a)
         language.add(x_a_c)