diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index c2ed79fd..993201eb 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -303,7 +303,7 @@ pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
     /* only allocate memory for the pbuf structure */
     p = memp_mallocp(MEMP_PBUF);
     if (p == NULL) {
-      DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_ROM/REF.\n"));
+      DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n", flag == PBUF_ROM?"ROM":"REF"));
       return NULL;
     }
     /* caller must set this field properly, afterwards */