diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index 55a0bf01..50b22c35 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -200,7 +200,8 @@ pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
     LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
                 ((u8_t*)p->payload + p->len <=
                  (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
-    LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT", p->len != 0);
+    LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT",
+      (PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset)) > 0 );
     /* set reference count (needed here in case we fail) */
     p->ref = 1;