diff --git a/mm/mm_heap/mm_foreach.c b/mm/mm_heap/mm_foreach.c
index 9be84a9848..a0d4dc9e57 100644
--- a/mm/mm_heap/mm_foreach.c
+++ b/mm/mm_heap/mm_foreach.c
@@ -81,6 +81,7 @@ void mm_foreach(FAR struct mm_heap_s *heap, mm_node_handler_t handler,
            node = (FAR struct mm_allocnode_s *)((FAR char *)node + nodesize))
         {
           nodesize = MM_SIZEOF_NODE(node);
+          DEBUGASSERT(nodesize >= MM_SIZEOF_ALLOCNODE);
           minfo("region=%d node=%p size=%zu preceding=%u (%c %c)\n",
                 region, node, nodesize, (unsigned int)node->preceding,
                 MM_PREVNODE_IS_FREE(node) ? 'F' : 'A',
diff --git a/tools/gdb/nuttxgdb/mm.py b/tools/gdb/nuttxgdb/mm.py
index c0da309724..bb923ecd5e 100644
--- a/tools/gdb/nuttxgdb/mm.py
+++ b/tools/gdb/nuttxgdb/mm.py
@@ -466,6 +466,9 @@ class MMNode(gdb.Value, p.MMFreeNode):
 
     @property
     def nextnode(self) -> MMNode:
+        if not self.nodesize:
+            return None
+
         addr = int(self.address) + self.nodesize
         type = utils.lookup_type("struct mm_freenode_s").pointer()
         # Use gdb.Value for better performance
@@ -551,7 +554,7 @@ class MMHeap(Value, p.MMHeap):
     def nodes(self) -> Generator[MMNode, None, None]:
         for start, end in self.regions:
             node = start
-            while node.address <= end.address:
+            while node and node.address <= end.address:
                 yield node
                 node = node.nextnode