diff --git a/build.go b/build.go
index 663289dc..b3e4c508 100644
--- a/build.go
+++ b/build.go
@@ -24,7 +24,7 @@ import (
 	"github.com/blevesearch/vellum"
 )
 
-const Version uint32 = 15
+const Version uint32 = 16
 
 const Type string = "zap"
 
diff --git a/section.go b/section.go
index a069a325..0306846d 100644
--- a/section.go
+++ b/section.go
@@ -30,5 +30,4 @@ const (
 
 var segmentSections = map[uint16]section{
 	sectionInvertedIndex: &invertedIndexSection{},
-	sectionVectorIndex:   &vectorIndexSection{},
 }
diff --git a/section_vector_index.go b/section_vector_index.go
index 7d7673e8..646abe61 100644
--- a/section_vector_index.go
+++ b/section_vector_index.go
@@ -1,6 +1,7 @@
-package zap
+//go:build densevector
+// +build densevector
 
-// keep a build tag for this file.
+package zap
 
 import (
 	"encoding/binary"
@@ -11,6 +12,10 @@ import (
 	faiss "github.com/blevesearch/go-faiss"
 )
 
+func init() {
+	segmentSections[sectionVectorIndex] = &vectorIndexSection{}
+}
+
 type vectorIndexSection struct {
 }
 
diff --git a/vector_search.go b/vector_search.go
index 1b6d0f72..7e3c3f7e 100644
--- a/vector_search.go
+++ b/vector_search.go
@@ -1,3 +1,6 @@
+//go:build densevector
+// +build densevector
+
 package zap
 
 import (
diff --git a/vector_test.go b/vector_test.go
index 1da247b8..dee34814 100644
--- a/vector_test.go
+++ b/vector_test.go
@@ -1,3 +1,6 @@
+//go:build densevector
+// +build densevector
+
 package zap
 
 import (