diff --git a/storage/default-dir-piece-completion-boltdb.go b/storage/default-dir-piece-completion-boltdb.go
new file mode 100644
index 00000000..a1e869a2
--- /dev/null
+++ b/storage/default-dir-piece-completion-boltdb.go
@@ -0,0 +1,11 @@
+// Bolt piece completion is available, and sqlite is not.
+//go:build !noboltdb && !wasm && (js || nosqlite)
+// +build !noboltdb
+// +build !wasm
+// +build js nosqlite
+
+package storage
+
+func NewDefaultPieceCompletionForDir(dir string) (PieceCompletion, error) {
+	return NewBoltPieceCompletion(dir)
+}
diff --git a/storage/default-dir-piece-completion-other.go b/storage/default-dir-piece-completion-other.go
index 4e40e397..b6f561ca 100644
--- a/storage/default-dir-piece-completion-other.go
+++ b/storage/default-dir-piece-completion-other.go
@@ -1,5 +1,6 @@
-//go:build wasm
-// +build wasm
+// Bolt piece completion is not available, and neither is sqlite.
+//go:build wasm || noboltdb
+// +build wasm noboltdb
 
 package storage
 
diff --git a/storage/default-dir-piece-completion-sqlite.go b/storage/default-dir-piece-completion-sqlite.go
deleted file mode 100644
index 8f4fbd4c..00000000
--- a/storage/default-dir-piece-completion-sqlite.go
+++ /dev/null
@@ -1,8 +0,0 @@
-//go:build !nosqlite
-// +build !nosqlite
-
-package storage
-
-func NewDefaultPieceCompletionForDir(dir string) (PieceCompletion, error) {
-	return NewSqlitePieceCompletion(dir)
-}
diff --git a/storage/sqlite-piece-completion.go b/storage/sqlite-piece-completion.go
index 54331e32..30c8a388 100644
--- a/storage/sqlite-piece-completion.go
+++ b/storage/sqlite-piece-completion.go
@@ -1,5 +1,7 @@
-//go:build !nosqlite
-// +build !nosqlite
+// modernc.org/sqlite depends on modernc.org/libc which doesn't work for JS (and probably wasm but I
+// think JS is the stronger signal).
+//go:build !js && !nosqlite
+// +build !js,!nosqlite
 
 package storage
 
@@ -13,6 +15,11 @@ import (
 	"zombiezen.com/go/sqlite/sqlitex"
 )
 
+// sqlite is always the default when available.
+func NewDefaultPieceCompletionForDir(dir string) (PieceCompletion, error) {
+	return NewSqlitePieceCompletion(dir)
+}
+
 type sqlitePieceCompletion struct {
 	mu     sync.Mutex
 	closed bool