diff --git a/cql3/expr/prepare_expr.cc b/cql3/expr/prepare_expr.cc
index 17392047f7..9461c71891 100644
--- a/cql3/expr/prepare_expr.cc
+++ b/cql3/expr/prepare_expr.cc
@@ -995,6 +995,9 @@ test_assignment(const expression& expr, data_dictionary::database db, const sstr
         [&] (const column_value&) -> test_result {
             on_internal_error(expr_logger, "column_values are not yet reachable via test_assignment()");
         },
+        [&] (const subscript&) -> test_result {
+            on_internal_error(expr_logger, "subscripts are not yet reachable via test_assignment()");
+        },
         [&] (const token&) -> test_result {
             on_internal_error(expr_logger, "tokens are not yet reachable via test_assignment()");
         },