diff --git a/Machines/Apple/AppleIIgs/MemoryMap.hpp b/Machines/Apple/AppleIIgs/MemoryMap.hpp
index 6d1820caf..00c4a4355 100644
--- a/Machines/Apple/AppleIIgs/MemoryMap.hpp
+++ b/Machines/Apple/AppleIIgs/MemoryMap.hpp
@@ -11,6 +11,7 @@
 
 #include <array>
 #include <bitset>
+#include <cassert>
 #include <vector>
 
 #include "../AppleII/LanguageCardSwitches.hpp"