diff --git a/mex/sources/bytecode/Evaluate.hh b/mex/sources/bytecode/Evaluate.hh
index 8f46af0b83863c07cead5268e61e94e9adc894b4..1fb87581c0ab010337f7add6d2fda0c2b4cc1562 100644
--- a/mex/sources/bytecode/Evaluate.hh
+++ b/mex/sources/bytecode/Evaluate.hh
@@ -23,6 +23,7 @@
 #include <vector>
 #include <string>
 #include <map>
+#include <optional>
 
 #define BYTECODE_MEX
 #include "Bytecode.hh"