diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index a9e33da01d1..7300429fe03 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -140,7 +140,8 @@ bool Moc::parseClassHead(ClassDef *def)
             }
         } while (test(COMMA));
 
-        if (knownGadgets.contains(def->superclassList.first().first)) {
+        if (!def->superclassList.isEmpty()
+            && knownGadgets.contains(def->superclassList.first().first)) {
             // Q_GADGET subclasses are treated as Q_GADGETs
             knownGadgets.insert(def->classname, def->qualified);
             knownGadgets.insert(def->qualified, def->qualified);
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index 08dc9581e16..00e5c60b29c 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -83,6 +83,10 @@ QT_USE_NAMESPACE
 template <bool b> struct QTBUG_31218 {};
 struct QTBUG_31218_Derived : QTBUG_31218<-1<0> {};
 
+#if defined(Q_MOC_RUN)
+ class QTBUG_45790 : Bug() { };
+#endif
+
 struct MyStruct {};
 struct MyStruct2 {};