diff --git a/src/emu/emu.h b/src/emu/emu.h
index 120615187db..54a3b2787ad 100644
--- a/src/emu/emu.h
+++ b/src/emu/emu.h
@@ -21,6 +21,7 @@
 #include <list>
 #include <vector>
 #include <memory>
+#include <map>
 #include <unordered_map>
 #include <unordered_set>
 
diff --git a/src/emu/ioport.h b/src/emu/ioport.h
index 455ef660e60..ea5415dd343 100644
--- a/src/emu/ioport.h
+++ b/src/emu/ioport.h
@@ -1265,7 +1265,7 @@ struct ioport_field_live
 // ======================> ioport_list
 
 // class that holds a list of I/O ports
-class ioport_list : public std::unordered_map<std::string, std::unique_ptr<ioport_port>>
+class ioport_list : public std::map<std::string, std::unique_ptr<ioport_port>>
 {
 	DISABLE_COPYING(ioport_list);