diff --git a/internal/manifest/iso_tree.go b/internal/manifest/iso_tree.go
index 19b4be769..846551d8e 100644
--- a/internal/manifest/iso_tree.go
+++ b/internal/manifest/iso_tree.go
@@ -140,7 +140,7 @@ func (p *ISOTree) serialize() osbuild.Pipeline {
 	filename := "images/efiboot.img"
 	pipeline.AddStage(osbuild.NewTruncateStage(&osbuild.TruncateStageOptions{
 		Filename: filename,
-		Size:     "20MB",
+		Size:     fmt.Sprintf("%d", p.PartitionTable.Size),
 	}))
 
 	efibootDevice := osbuild.NewLoopbackDevice(&osbuild.LoopbackDeviceOptions{Filename: filename})