diff --git a/sys/i386/include/param.h b/sys/i386/include/param.h
index c1e14245b635..b494f35095d0 100644
--- a/sys/i386/include/param.h
+++ b/sys/i386/include/param.h
@@ -122,6 +122,20 @@
 #endif
 #define KSTACK_GUARD_PAGES 1	/* pages of kstack guard; 0 disables */
 
+/*
+ * Ceiling on amount of swblock kva space, can be changed via
+ * the kern.maxswzone /boot/loader.conf variable.
+ *
+ * 276 is sizeof(struct swblock), but we do not always have a definition
+ * in scope for struct swblock, so we have to hardcode it.  Each struct
+ * swblock holds metadata for 32 pages, so in theory, this is enough for
+ * 16 GB of swap.  In practice, however, the usable amount is considerably
+ * lower due to fragmentation.
+ */
+#ifndef VM_SWZONE_SIZE_MAX
+#define VM_SWZONE_SIZE_MAX	(276 * 128 * 1024)
+#endif
+
 /*
  * Ceiling on size of buffer cache (really only effects write queueing,
  * the VM page cache is not effected), can be changed via