diff --git a/cddl/compat/opensolaris/include/libproc.h b/cddl/compat/opensolaris/include/libproc.h
--- a/cddl/compat/opensolaris/include/libproc.h
+++ b/cddl/compat/opensolaris/include/libproc.h
@@ -35,8 +35,9 @@
 #define ps_prochandle	proc_handle
 #define Lmid_t		int
 
-#define PR_RLC		0x0001
-#define PR_KLC		0x0002
+/* These must not collide with proc_attach() flags in lib/libproc/libproc.h. */
+#define PR_RLC		0x010000
+#define PR_KLC		0x020000
 
 #include_next <libproc.h>
 
diff --git a/lib/libproc/libproc.h b/lib/libproc/libproc.h
--- a/lib/libproc/libproc.h
+++ b/lib/libproc/libproc.h
@@ -52,7 +52,11 @@
 #define PS_DEAD		5
 #define PS_LOST		6
 
-/* Flags for proc_attach(). */
+/*
+ * Flags for proc_attach().
+ *
+ * When adding flags, see cddl/compat/opensolaris/include/libproc.h.
+ */
 #define	PATTACH_FORCE	0x01
 #define	PATTACH_RDONLY	0x02
 #define	PATTACH_NOSTOP	0x04