diff --git a/subprojects/libvhost-user/libvhost-user.h b/subprojects/libvhost-user/libvhost-user.h
index c882b4e3a2..deb40e77b3 100644
--- a/subprojects/libvhost-user/libvhost-user.h
+++ b/subprojects/libvhost-user/libvhost-user.h
@@ -31,10 +31,12 @@
 #define VHOST_MEMORY_BASELINE_NREGIONS 8
 
 /*
- * Set a reasonable maximum number of ram slots, which will be supported by
- * any architecture.
+ * vhost in the kernel usually supports 509 mem slots. 509 used to be the
+ * KVM limit, it supported 512, but 3 were used for internal purposes. This
+ * limit is sufficient to support many DIMMs and virtio-mem in
+ * "dynamic-memslots" mode.
  */
-#define VHOST_USER_MAX_RAM_SLOTS 32
+#define VHOST_USER_MAX_RAM_SLOTS 509
 
 #define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)