diff --git a/os/hal/lib/streams/memstreams.c b/os/hal/lib/streams/memstreams.c
index a4a2fb4a4..6bbd66cef 100644
--- a/os/hal/lib/streams/memstreams.c
+++ b/os/hal/lib/streams/memstreams.c
@@ -84,7 +84,7 @@ static msg_t _get(void *ip) {
   return b;
 }
 
-static const struct MemStreamVMT vmt = {_writes, _reads, _put, _get};
+static const struct MemStreamVMT vmt = {(size_t)0, _writes, _reads, _put, _get};
 
 /*===========================================================================*/
 /* Driver exported functions.                                                */
diff --git a/os/hal/lib/streams/nullstreams.c b/os/hal/lib/streams/nullstreams.c
index d21ecd990..c15455b22 100644
--- a/os/hal/lib/streams/nullstreams.c
+++ b/os/hal/lib/streams/nullstreams.c
@@ -73,7 +73,7 @@ static msg_t get(void *ip) {
   return 4;
 }
 
-static const struct NullStreamVMT vmt = {writes, reads, put, get};
+static const struct NullStreamVMT vmt = {(size_t)0, writes, reads, put, get};
 
 /*===========================================================================*/
 /* Driver exported functions.                                                */