diff --git a/Sources/Containerization/ContainerManager.swift b/Sources/Containerization/ContainerManager.swift
index 1b3a4089b..27e9fbe47 100644
--- a/Sources/Containerization/ContainerManager.swift
+++ b/Sources/Containerization/ContainerManager.swift
@@ -342,7 +342,7 @@ public struct ContainerManager: Sendable {
 
     private func unpack(image: Image, destination: URL, size: UInt64, progress: ProgressHandler? = nil) async throws -> Mount {
         do {
-            let unpacker = EXT4Unpacker(blockSizeInBytes: size)
+            let unpacker = EXT4Unpacker(capacityInBytes: size)
             return try await unpacker.unpack(image, for: .current, at: destination, progress: progress)
         } catch let err as ContainerizationError {
             if err.code == .exists {
diff --git a/Sources/Containerization/Image/InitImage.swift b/Sources/Containerization/Image/InitImage.swift
index a63f0dce2..5a4ef58ba 100644
--- a/Sources/Containerization/Image/InitImage.swift
+++ b/Sources/Containerization/Image/InitImage.swift
@@ -34,7 +34,7 @@ public struct InitImage: Sendable {
 extension InitImage {
     /// Unpack the initial filesystem for the desired platform at a given path.
     public func initBlock(at: URL, for platform: SystemPlatform) async throws -> Mount {
-        let unpacker = EXT4Unpacker(blockSizeInBytes: 512.mib())
+        let unpacker = EXT4Unpacker(capacityInBytes: 512.mib())
         var fs = try await unpacker.unpack(self.image, for: platform.ociPlatform(), at: at)
         fs.options = ["ro"]
         return fs
diff --git a/Sources/Containerization/Image/Unpacker/EXT4Unpacker.swift b/Sources/Containerization/Image/Unpacker/EXT4Unpacker.swift
index 0e9609b9a..2c96617cf 100644
--- a/Sources/Containerization/Image/Unpacker/EXT4Unpacker.swift
+++ b/Sources/Containerization/Image/Unpacker/EXT4Unpacker.swift
@@ -23,16 +23,16 @@ import Foundation
 import SystemPackage
 
 public struct EXT4Unpacker: Unpacker {
-    let blockSizeInBytes: UInt64
+    let capacityInBytes: UInt64
 
     let journal: EXT4.JournalConfig?
 
     /// Creates an unpacker that extracts images into EXT4 filesystems.
     /// - Parameters:
-    ///   - blockSizeInBytes: The filesystem block size.
+    ///   - capacityInBytes: The minimum usable capacity of the filesystem image, in bytes.
     ///   - journal: The journal configuration to use, or nil for no journaling.
-    public init(blockSizeInBytes: UInt64, journal: EXT4.JournalConfig? = nil) {
-        self.blockSizeInBytes = blockSizeInBytes
+    public init(capacityInBytes: UInt64, journal: EXT4.JournalConfig? = nil) {
+        self.capacityInBytes = capacityInBytes
         self.journal = journal
     }
 
@@ -49,7 +49,7 @@ public struct EXT4Unpacker: Unpacker {
         let cleanedPath = try prepareUnpackPath(path: path)
         let filesystem = try EXT4.Formatter(
             FilePath(cleanedPath),
-            minDiskSize: blockSizeInBytes,
+            minDiskSize: capacityInBytes,
             journal: journal
         )
         defer { try? filesystem.close() }
@@ -79,7 +79,7 @@ public struct EXT4Unpacker: Unpacker {
             FilePath(
                 cleanedPath
             ),
-            minDiskSize: blockSizeInBytes
+            minDiskSize: capacityInBytes
         )
         defer { try? filesystem.close() }
 
diff --git a/Sources/Integration/Suite.swift b/Sources/Integration/Suite.swift
index 440384ea0..a3c11977f 100644
--- a/Sources/Integration/Suite.swift
+++ b/Sources/Integration/Suite.swift
@@ -236,7 +236,7 @@ struct IntegrationSuite: AsyncParsableCommand {
         let fsPath = Self.testDir.appending(component: image.digest)
         let fs = try await Self.unpackCoordinator.unpack(key: fsPath.absolutePath()) {
             do {
-                let unpacker = EXT4Unpacker(blockSizeInBytes: 2.gib())
+                let unpacker = EXT4Unpacker(capacityInBytes: 2.gib())
                 return try await unpacker.unpack(image, for: platform, at: fsPath)
             } catch let err as ContainerizationError {
                 if err.code == .exists {
diff --git a/Sources/cctl/ImageCommand.swift b/Sources/cctl/ImageCommand.swift
index 6247067b3..6f9eba1a0 100644
--- a/Sources/cctl/ImageCommand.swift
+++ b/Sources/cctl/ImageCommand.swift
@@ -146,7 +146,7 @@ extension Application {
                 let unpackUrl = URL(filePath: unpackPath)
                 try FileManager.default.createDirectory(at: unpackUrl, withIntermediateDirectories: true)
 
-                let unpacker = EXT4Unpacker.init(blockSizeInBytes: 2.gib())
+                let unpacker = EXT4Unpacker.init(capacityInBytes: 2.gib())
 
                 startTime = ContinuousClock.now
                 if let platform {
diff --git a/Sources/cctl/RootfsCommand.swift b/Sources/cctl/RootfsCommand.swift
index cd5fd36f8..2145d61dd 100644
--- a/Sources/cctl/RootfsCommand.swift
+++ b/Sources/cctl/RootfsCommand.swift
@@ -95,7 +95,7 @@ extension Application {
             }
 
             private func outputExt4(archive: URL, to path: URL) async throws {
-                let unpacker = EXT4Unpacker(blockSizeInBytes: 256.mib())
+                let unpacker = EXT4Unpacker(capacityInBytes: 256.mib())
                 try await unpacker.unpack(archive: archive, compression: .gzip, at: path)
             }
 
diff --git a/Sources/cctl/RunCommand.swift b/Sources/cctl/RunCommand.swift
index cc5a00a42..fceff1724 100644
--- a/Sources/cctl/RunCommand.swift
+++ b/Sources/cctl/RunCommand.swift
@@ -352,7 +352,7 @@ extension Application {
 
             var rootfsMount: Containerization.Mount
             do {
-                let unpacker = EXT4Unpacker(blockSizeInBytes: fsSizeInMB.mib())
+                let unpacker = EXT4Unpacker(capacityInBytes: fsSizeInMB.mib())
                 rootfsMount = try await unpacker.unpack(image, for: imagePlatform, at: rootfsPath)
             } catch let err as ContainerizationError where err.code == .exists {
                 rootfsMount = .block(