diff --git a/README.md b/README.md
index dc15748..af32efa 100644
--- a/README.md
+++ b/README.md
@@ -145,6 +145,9 @@ VM = "boot2docker-vm"
 # path to boot2docker ISO image
 ISO = "/Users/sven/.boot2docker/boot2docker.iso"
 
+# when non-empty, URL to fetch the custom boot2docker ISO image from
+URLCustomISO = "http://internal.corp.org/b2d.iso"
+
 # VM disk image size in MB
 DiskSize = 20000
 
diff --git a/cmds.go b/cmds.go
index f82c979..8a5cc96 100644
--- a/cmds.go
+++ b/cmds.go
@@ -406,15 +406,21 @@ func cmdIP() error {
 
 // Download the boot2docker ISO image.
 func cmdDownload() error {
-	fmt.Println("Downloading boot2docker ISO image...")
-	url := "https://api.github.com/repos/boot2docker/boot2docker/releases"
-	tag, err := getLatestReleaseName(url)
-	if err != nil {
-		return fmt.Errorf("Failed to get latest release: %s", err)
-	}
-	fmt.Printf("Latest release is %s\n", tag)
+	url := ""
+	if B2D.URLCustomISO == "" {
+		url = "https://api.github.com/repos/boot2docker/boot2docker/releases"
+		tag, err := getLatestReleaseName(url)
+		if err != nil {
+			return fmt.Errorf("Failed to get latest release: %s", err)
+		}
+		fmt.Printf("Latest release is %s\n", tag)
 
-	url = fmt.Sprintf("https://github.com/boot2docker/boot2docker/releases/download/%s/boot2docker.iso", tag)
+		fmt.Println("Downloading latest official boot2docker ISO image...")
+		url = fmt.Sprintf("https://github.com/boot2docker/boot2docker/releases/download/%s/boot2docker.iso", tag)
+	} else {
+		fmt.Println("Downloading custom boot2docker ISO image...")
+		url = B2D.URLCustomISO
+	}
 	if err := download(B2D.ISO, url); err != nil {
 		return fmt.Errorf("Failed to download ISO image: %s", err)
 	}
diff --git a/config.go b/config.go
index 99db276..80fbd73 100644
--- a/config.go
+++ b/config.go
@@ -92,6 +92,7 @@ func config() (*flag.FlagSet, error) {
 	//flags.StringVarP(&B2D.Dir, "dir", "d", dir, "boot2docker config directory.")
 	B2D.Dir = dir
 	flags.StringVar(&B2D.ISO, "iso", filepath.Join(dir, "boot2docker.iso"), "path to boot2docker ISO image.")
+	flags.StringVar(&B2D.URLCustomISO, "urlcustomiso", "", "URL of a custom boot2docker ISO to download instead of the official one.")
 
 	// Sven disabled this, as it is broken - if I user with a fresh computer downloads
 	// just the boot2docker-cli, and then runs `boot2docker --init ip`, we create a vm
diff --git a/driver/config.go b/driver/config.go
index 5d11167..20f33d7 100644
--- a/driver/config.go
+++ b/driver/config.go
@@ -14,14 +14,15 @@ type MachineConfig struct {
 	Driver  string
 
 	// basic config
-	SSH      string // SSH client executable
-	SSHGen   string // SSH keygen executable
-	SSHKey   string // SSH key to send to the vm
-	VM       string // virtual machine name
-	Dir      string // boot2docker directory
-	ISO      string // boot2docker ISO image path
-	DiskSize uint   // VM disk image size (MB)
-	Memory   uint   // VM memory size (MB)
+	SSH          string // SSH client executable
+	SSHGen       string // SSH keygen executable
+	SSHKey       string // SSH key to send to the vm
+	VM           string // virtual machine name
+	Dir          string // boot2docker directory
+	ISO          string // boot2docker ISO image path
+	URLCustomISO string // custom ISO image URL
+	DiskSize     uint   // VM disk image size (MB)
+	Memory       uint   // VM memory size (MB)
 
 	// NAT network: port forwarding
 	SSHPort    uint16 // host SSH port (forward to port 22 in VM)