diff --git a/parser_library/src/expressions/conditional_assembly/ca_operator_unary.cpp b/parser_library/src/expressions/conditional_assembly/ca_operator_unary.cpp
index c301797a7..6e3477f79 100644
--- a/parser_library/src/expressions/conditional_assembly/ca_operator_unary.cpp
+++ b/parser_library/src/expressions/conditional_assembly/ca_operator_unary.cpp
@@ -66,7 +66,7 @@ void ca_function_unary_operator::resolve_expression_tree(ca_expression_ctx expr_
     expr_kind = expr_ctx.kind;
     m_expr_ctx = expr_ctx;
     expr_ctx.kind = ca_common_expr_policy::get_operands_type(function, expr_ctx.kind);
-    expr->resolve_expression_tree(m_expr_ctx, diags);
+    expr->resolve_expression_tree(expr_ctx, diags);
 }
 
 context::SET_t ca_function_unary_operator::operation(context::SET_t operand, const evaluation_context& eval_ctx) const
diff --git a/parser_library/test/expressions/character_expression_test.cpp b/parser_library/test/expressions/character_expression_test.cpp
index d1d15b179..acda5366e 100644
--- a/parser_library/test/expressions/character_expression_test.cpp
+++ b/parser_library/test/expressions/character_expression_test.cpp
@@ -323,4 +323,33 @@ TEST(character_expression, invalid_expression)
 //
 //    EXPECT_TRUE(a.diags().empty());
 //    EXPECT_EQ(get_var_value<C_t>(a.hlasm_ctx(), "C"), "VENFG");
-//}
\ No newline at end of file
+//}
+
+TEST(character_expression, valid_function)
+{
+    std::string input =
+        R"(
+&A      SETA  210
+&C      SETC (BYTE &A)
+)";
+    analyzer a(input);
+    a.analyze();
+    a.collect_diags();
+
+    EXPECT_TRUE(a.diags().empty());
+    EXPECT_EQ(get_var_value<C_t>(a.hlasm_ctx(), "C"), "K");
+}
+
+TEST(character_expression, invalid_function)
+{
+    std::string input =
+        R"(
+&A      SETC  'X'
+&C      SETC (BYTE &A)
+)";
+    analyzer a(input);
+    a.analyze();
+    a.collect_diags();
+
+    EXPECT_TRUE(matches_message_codes(a.diags(), { "CE012" }));
+}
\ No newline at end of file