diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index 1ebd542b..fe53defd 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -2125,7 +2125,7 @@
 #endif
 #if !PPPOS_SUPPORT || !PPP_IPV4_SUPPORT
 #undef VJ_SUPPORT
-#define VJ_SUPPORT                      0   /* VJ compression is only supported for PPPoS. */
+#define VJ_SUPPORT                      0   /* VJ compression is only supported for IPv4 over PPPoS. */
 #endif /* !PPPOS_SUPPORT */
 
 /**