diff --git a/src/arch/x86/drivers/hyperv/hyperv.c b/src/arch/x86/drivers/hyperv/hyperv.c
index 4e687687..1903d1db 100644
--- a/src/arch/x86/drivers/hyperv/hyperv.c
+++ b/src/arch/x86/drivers/hyperv/hyperv.c
@@ -220,6 +220,29 @@ static int hv_check_features ( struct hv_hypervisor *hv ) {
 	return 0;
 }
 
+/**
+ * Check that Gen 2 UEFI firmware is not running
+ *
+ * @v hv		Hyper-V hypervisor
+ * @ret rc		Return status code
+ *
+ * We must not steal ownership from the Gen 2 UEFI firmware, since
+ * doing so will cause an immediate crash.  Avoid this by checking for
+ * the guest OS identity known to be used by the Gen 2 UEFI firmware.
+ */
+static int hv_check_uefi ( struct hv_hypervisor *hv ) {
+	uint64_t guest_os_id;
+
+	/* Check for UEFI firmware's guest OS identity */
+	guest_os_id = rdmsr ( HV_X64_MSR_GUEST_OS_ID );
+	if ( guest_os_id == HV_GUEST_OS_ID_UEFI ) {
+		DBGC ( hv, "HV %p is owned by UEFI firmware\n", hv );
+		return -ENOTSUP;
+	}
+
+	return 0;
+}
+
 /**
  * Map hypercall page
  *
@@ -556,6 +579,10 @@ static int hv_probe ( struct root_device *rootdev ) {
 	if ( ( rc = hv_check_features ( hv ) ) != 0 )
 		goto err_check_features;
 
+	/* Check that Gen 2 UEFI firmware is not running */
+	if ( ( rc = hv_check_uefi ( hv ) ) != 0 )
+		goto err_check_uefi;
+
 	/* Allocate pages */
 	if ( ( rc = hv_alloc_pages ( hv, &hv->hypercall, &hv->synic.message,
 				     &hv->synic.event, NULL ) ) != 0 )
@@ -587,6 +614,7 @@ static int hv_probe ( struct root_device *rootdev ) {
 	hv_free_pages ( hv, hv->hypercall, hv->synic.message, hv->synic.event,
 			NULL );
  err_alloc_pages:
+ err_check_uefi:
  err_check_features:
 	free ( hv );
  err_alloc:
diff --git a/src/include/ipxe/hyperv.h b/src/include/ipxe/hyperv.h
index 9194a976..9b7e54a5 100644
--- a/src/include/ipxe/hyperv.h
+++ b/src/include/ipxe/hyperv.h
@@ -37,6 +37,13 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  */
 #define HV_GUEST_OS_ID_IPXE ( ( 1ULL << 63 ) | ( 0x18aeULL << 48 ) )
 
+/** Guest OS identity for Gen 2 UEFI firmware
+ *
+ * This does not conform to the documented structure for guest OS
+ * identities.
+ */
+#define HV_GUEST_OS_ID_UEFI ( 1ULL << 40 )
+
 /** Enable hypercall page */
 #define HV_HYPERCALL_ENABLE 0x00000001UL