diff --git a/sys/sys/_types.h b/sys/sys/_types.h
--- a/sys/sys/_types.h
+++ b/sys/sys/_types.h
@@ -155,6 +155,14 @@
 typedef int		__cpusetid_t;	/* cpuset identifier. */
 typedef __int64_t	__daddr_t;	/* bwrite(3), FIOBMAP2, etc */
 
+/*
+ * Support non-CHERI-aware ABIs by defining __intcap_t.
+ */
+#if !__has_feature(capabilities)
+typedef	__intptr_t	__intcap_t;
+typedef	__uintptr_t	__uintcap_t;
+#endif
+
 /*
  * Unusual type definitions.
  */