diff --git a/bucket.go b/bucket.go
index 25ad1ba..a57f456 100644
--- a/bucket.go
+++ b/bucket.go
@@ -476,6 +476,7 @@ func (b *Bucket) spill() error {
 	b.rootNode = b.rootNode.root()
 
 	// Update the root node for this bucket.
+	_assert(b.rootNode.pgid < b.tx.meta.pgid, "pgid (%d) above high water mark (%d)", b.rootNode.pgid, b.tx.meta.pgid)
 	b.root = b.rootNode.pgid
 
 	return nil
diff --git a/db.go b/db.go
index d96a161..0b74621 100644
--- a/db.go
+++ b/db.go
@@ -705,6 +705,10 @@ func (m *meta) copy(dest *meta) {
 
 // write writes the meta onto a page.
 func (m *meta) write(p *page) {
+
+	_assert(m.root.root < m.pgid, "root bucket pgid (%d) above high water mark (%d)", m.root.root, m.pgid)
+	_assert(m.freelist < m.pgid, "freelist pgid (%d) above high water mark (%d)", m.freelist, m.pgid)
+
 	// Page id is either going to be 0 or 1 which we can determine by the transaction ID.
 	p.id = pgid(m.txid % 2)
 	p.flags |= metaPageFlag
diff --git a/node.go b/node.go
index 1bc889d..14bf136 100644
--- a/node.go
+++ b/node.go
@@ -98,6 +98,8 @@ func (n *node) prevSibling() *node {
 
 // put inserts a key/value.
 func (n *node) put(oldKey, newKey, value []byte, pgid pgid, flags uint32) {
+	_assert(pgid < n.bucket.tx.meta.pgid, "pgid (%d) above high water mark (%d)", pgid, n.bucket.tx.meta.pgid)
+
 	// Find insertion index.
 	index := sort.Search(len(n.inodes), func(i int) bool { return bytes.Compare(n.inodes[i].key, oldKey) != -1 })
 
@@ -278,6 +280,7 @@ func (n *node) spill() error {
 		}
 
 		// Write the node.
+		_assert(p.id < tx.meta.pgid, "pgid (%d) above high water mark (%d)", p.id, tx.meta.pgid)
 		node.pgid = p.id
 		node.write(p)
 
@@ -307,6 +310,7 @@ func (n *node) spill() error {
 		}
 
 		// Write the new root.
+		_assert(p.id < tx.meta.pgid, "pgid (%d) above high water mark (%d)", p.id, tx.meta.pgid)
 		parent.pgid = p.id
 		parent.write(p)
 	}