diff --git a/src/drivers/net/efi/snponly.c b/src/drivers/net/efi/snponly.c
index d8dc86ad2..d454ed20b 100644
--- a/src/drivers/net/efi/snponly.c
+++ b/src/drivers/net/efi/snponly.c
@@ -20,16 +20,28 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <errno.h>
+#include <ipxe/init.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/efi_driver.h>
+#include <ipxe/efi/Protocol/SimpleNetwork.h>
 #include "snpnet.h"
 
 /** @file
  *
- * SNP chainloaded-device-only driver
+ * SNP chainloading-device-only driver
  *
  */
 
+/**
+ * SNP protocol instance installed on the loaded image's device handle
+ *
+ * We match against the SNP protocol instance (rather than simply
+ * matching against the device handle itself) because some systems
+ * load us via a child of the SNP device, with a duplicate SNP
+ * protocol installed on the child handle.
+ */
+static EFI_SIMPLE_NETWORK_PROTOCOL *snponly;
+
 /**
  * Check to see if driver supports a device
  *
@@ -37,21 +49,90 @@ FILE_LICENCE ( GPL2_OR_LATER );
  * @ret rc		Return status code
  */
 static int snponly_supported ( EFI_HANDLE device ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_STATUS efirc;
+	union {
+		EFI_SIMPLE_NETWORK_PROTOCOL *snp;
+		void *interface;
+	} snp;
+	int rc;
 
-	/* Check that this device is our loaded image's device */
-	if ( device != efi_loaded_image->DeviceHandle )
-		return -ENOTTY;
+	/* Get SNP protocol */
+	if ( ( efirc = bs->OpenProtocol ( device,
+					  &efi_simple_network_protocol_guid,
+					  &snp.interface, efi_image_handle,
+					  device,
+					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
+		rc = -EEFI ( efirc );
+		DBGCP ( device, "SNPONLY %p %s is not an SNP device\n",
+			device, efi_handle_name ( device ) );
+		goto err_not_snp;
+	}
 
-	DBGC ( device, "SNP %p %s is the SNP chainloading device\n",
-	       device, efi_handle_name ( device ) );
+	/* Test for a match against the chainloading device */
+	if ( snp.snp != snponly ) {
+		DBGC ( device, "SNPONLY %p %s SNP %p is not the "
+		       "chainloading SNP\n", device,
+		       efi_handle_name ( device ), snp.snp );
+		rc = -ENOTTY;
+		goto err_not_snponly;
+	}
 
-	return 0;
+	/* Success */
+	rc = 0;
+	DBGC ( device, "SNPONLY %p %s SNP %p is the chainloading SNP\n",
+	       device, efi_handle_name ( device ), snp.snp );
+
+ err_not_snponly:
+	bs->CloseProtocol ( device, &efi_simple_network_protocol_guid,
+			    efi_image_handle, device );
+ err_not_snp:
+	return rc;
 }
 
-/** EFI SNP driver */
+/** EFI chainloading-device-only driver */
 struct efi_driver snponly_driver __efi_driver ( EFI_DRIVER_NORMAL ) = {
 	.name = "SNPONLY",
 	.supported = snponly_supported,
 	.start = snpnet_start,
 	.stop = snpnet_stop,
 };
+
+/**
+ * Initialise EFI chainloading-device-only driver
+ *
+ */
+static void snponly_init ( void ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	EFI_HANDLE device = efi_loaded_image->DeviceHandle;
+	union {
+		EFI_SIMPLE_NETWORK_PROTOCOL *snp;
+		void *interface;
+	} snp;
+	EFI_STATUS efirc;
+
+	/* Look for SNP protocol on the loaded image's device handle */
+	if ( ( efirc = bs->OpenProtocol ( device,
+					  &efi_simple_network_protocol_guid,
+					  &snp.interface, efi_image_handle,
+					  device,
+					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
+		DBGC ( device, "SNPONLY %p %s is not an SNP device\n",
+		       device, efi_handle_name ( device ) );
+		goto err_open_protocol;
+	}
+
+	/* Record SNP protocol instance */
+	snponly = snp.snp;
+	DBGC ( device, "SNPONLY %p %s found chainloading SNP %p\n",
+	       device, efi_handle_name ( device ), snponly );
+
+ err_open_protocol:
+	bs->CloseProtocol ( device, &efi_simple_network_protocol_guid,
+			    efi_image_handle, device );
+}
+
+/** EFI chainloading-device-only initialisation function */
+struct init_fn snponly_init_fn __init_fn ( INIT_LATE ) = {
+	.initialise = snponly_init,
+};