diff --git a/src/conf/snapshot_conf.c b/src/conf/snapshot_conf.c
index 43f984912e..be5deadc8c 100644
--- a/src/conf/snapshot_conf.c
+++ b/src/conf/snapshot_conf.c
@@ -535,7 +535,7 @@ virDomainSnapshotRedefineValidate(virDomainSnapshotDef *def,
         if (external)
             align_location = VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL;
 
-        if (virDomainSnapshotAlignDisks(def, align_location, true) < 0)
+        if (virDomainSnapshotAlignDisks(def, NULL, align_location, true) < 0)
             return -1;
     }
 
@@ -622,16 +622,22 @@ virDomainSnapshotDefAssignExternalNames(virDomainSnapshotDef *def)
 /**
  * virDomainSnapshotAlignDisks:
  * @snapdef: Snapshot definition to align
+ * @existingDomainDef: definition of the domain belonging to a redefined snapshot
  * @default_snapshot: snapshot location to assign to disks which don't have any
  * @uniform_internal_snapshot: Require that for an internal snapshot all disks
  *                             take part in the internal snapshot
  *
- * Align snapdef->disks to snapdef->parent.dom, filling in any missing disks or
+ * Align snapdef->disks to domain definition, filling in any missing disks or
  * snapshot state defaults given by the domain, with a fallback to
  * @default_snapshot. Ensure that there are no duplicate snapshot disk
  * definitions in @snapdef and there are no disks described in @snapdef but
  * missing from the domain definition.
  *
+ * By default the domain definition from @snapdef->parent.dom is used, but when
+ * redefining an existing snapshot the domain definition may be omitted in
+ * @snapdef. In such case callers must pass in the definition from the snapsot
+ * being redefined as @existingDomainDef. In all other cases callers pass NULL.
+ *
  * When @uniform_internal_snapshot is true and @default_snapshot is
  * VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL, all disks in @snapdef must take part
  * in the internal snapshot. This is for hypervisors where granularity of an
@@ -643,6 +649,7 @@ virDomainSnapshotDefAssignExternalNames(virDomainSnapshotDef *def)
  */
 int
 virDomainSnapshotAlignDisks(virDomainSnapshotDef *snapdef,
+                            virDomainDef *existingDomainDef,
                             virDomainSnapshotLocation default_snapshot,
                             bool uniform_internal_snapshot)
 {
@@ -653,6 +660,9 @@ virDomainSnapshotAlignDisks(virDomainSnapshotDef *snapdef,
     size_t oldndisks;
     size_t i;
 
+    if (!domdef)
+        domdef = existingDomainDef;
+
     if (!domdef) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("missing domain in snapshot"));
diff --git a/src/conf/snapshot_conf.h b/src/conf/snapshot_conf.h
index 505c9f785d..446d0870f4 100644
--- a/src/conf/snapshot_conf.h
+++ b/src/conf/snapshot_conf.h
@@ -126,6 +126,7 @@ char *virDomainSnapshotDefFormat(const char *uuidstr,
                                  virDomainXMLOption *xmlopt,
                                  unsigned int flags);
 int virDomainSnapshotAlignDisks(virDomainSnapshotDef *snapshot,
+                                virDomainDef *existingDomainDef,
                                 virDomainSnapshotLocation default_snapshot,
                                 bool uniform_internal_snapshot);
 
diff --git a/src/qemu/qemu_snapshot.c b/src/qemu/qemu_snapshot.c
index 48fa19cebd..797972f4d4 100644
--- a/src/qemu/qemu_snapshot.c
+++ b/src/qemu/qemu_snapshot.c
@@ -1675,7 +1675,7 @@ qemuSnapshotCreateAlignDisks(virDomainObj *vm,
                        VIR_DOMAIN_SNAPSHOT_LOCATION_NONE :
                        VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL);
     }
-    if (virDomainSnapshotAlignDisks(def, align_location, true) < 0)
+    if (virDomainSnapshotAlignDisks(def, NULL, align_location, true) < 0)
         return -1;
 
     return 0;
diff --git a/src/test/test_driver.c b/src/test/test_driver.c
index 44f06530b5..dde7bf1b8e 100644
--- a/src/test/test_driver.c
+++ b/src/test/test_driver.c
@@ -8736,7 +8736,7 @@ testDomainSnapshotAlignDisks(virDomainObj *vm,
                       VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL;
     }
 
-    return virDomainSnapshotAlignDisks(def, align_location, true);
+    return virDomainSnapshotAlignDisks(def, NULL, align_location, true);
 }
 
 static virDomainSnapshotPtr