diff --git a/src/qemu/qemu_backup.c b/src/qemu/qemu_backup.c
index fac6592366..14cf6bbef0 100644
--- a/src/qemu/qemu_backup.c
+++ b/src/qemu/qemu_backup.c
@@ -170,7 +170,7 @@ qemuBackupDiskDataCleanup(virDomainObjPtr vm,
 }
 
 
-static virJSONValuePtr
+virJSONValuePtr
 qemuBackupDiskPrepareOneBitmapsChain(virDomainMomentDefPtr *incremental,
                                      virStorageSourcePtr backingChain,
                                      virHashTablePtr blockNamedNodeData G_GNUC_UNUSED,
diff --git a/src/qemu/qemu_backup.h b/src/qemu/qemu_backup.h
index 0f76abe067..df67b849be 100644
--- a/src/qemu/qemu_backup.h
+++ b/src/qemu/qemu_backup.h
@@ -44,3 +44,10 @@ int
 qemuBackupGetJobInfoStats(virQEMUDriverPtr driver,
                           virDomainObjPtr vm,
                           qemuDomainJobInfoPtr jobInfo);
+
+/* exported for testing */
+virJSONValuePtr
+qemuBackupDiskPrepareOneBitmapsChain(virDomainMomentDefPtr *incremental,
+                                     virStorageSourcePtr backingChain,
+                                     virHashTablePtr blockNamedNodeData,
+                                     const char *diskdst);