--- afdko/c/addfeatures/hotconv/otl.cpp
+++ afdko/c/addfeatures/hotconv/otl.cpp
@@ -674,15 +674,15 @@ void OTL::prepLookupList() {
 
     auto prevl = subtables.begin();
     for (auto sl = prevl + 1; sl <= subtables.end(); sl++) {
-        auto &slr = *sl;
+        Subtable *slr = sl == subtables.end() ? nullptr : sl->get();
         auto &prevlr = *prevl;
-        if (sl == subtables.end() || slr->isRef() || slr->isParam() ||
+        if (slr == nullptr || slr->isRef() || slr->isParam() ||
             slr->index.lookup != prevlr->index.lookup) {
             /* Lookup index change */
             prevlr->span.lookup = sl;
             prevl = sl;
         }
-        if (sl != subtables.end() && (slr->isRef() || slr->isParam()))
+        if (slr != nullptr && (slr->isRef() || slr->isParam()))
             break;
     }
 }