diff --git a/metropolis/installer/main.go b/metropolis/installer/main.go
index 8aa8836..6313548 100644
--- a/metropolis/installer/main.go
+++ b/metropolis/installer/main.go
@@ -238,7 +238,7 @@
 	}
 	// Calculate the minimum target size based on the installation parameters.
 	minSize := uint64((installParams.PartitionSize.ESP +
-		installParams.PartitionSize.System +
+		installParams.PartitionSize.System*2 +
 		installParams.PartitionSize.Data + 1) * mib)
 
 	// Look for suitable block devices, given the minimum size.