diff --git a/src/script_opt/ZAM/ZOp.h b/src/script_opt/ZAM/ZOp.h
index 783facff36..f2fdebd36c 100644
--- a/src/script_opt/ZAM/ZOp.h
+++ b/src/script_opt/ZAM/ZOp.h
@@ -6,6 +6,7 @@
 
 #include <string>
 #include <unordered_map>
+#include <vector>
 
 namespace zeek::detail {