--- src/communityid.bif	2025-08-20 16:36:43.000000000 +0800
+++ src/communityid.bif	2026-08-20 00:00:00.000000000 +0800
@@ -4,6 +4,13 @@
 #include "zeek/Val.h"
 #include "zeek/digest.h"
 #include "zeek/packet_analysis/protocol/icmp/ICMP.h"
+
+// IPPROTO_SCTP is missing from system headers on macOS < 10.7. Define the
+// IANA protocol number instead of compiling the check below out, so that
+// Community ID values for SCTP flows stay identical to other platforms.
+#ifndef IPPROTO_SCTP
+#define IPPROTO_SCTP 132
+#endif
 %%}
 
 ## Compute the Community ID hash (v1) from a connection identifier.