diff --git a/core/src/main/java/google/registry/tools/UpdateReservedListCommand.java b/core/src/main/java/google/registry/tools/UpdateReservedListCommand.java
index a15797063..752f41887 100644
--- a/core/src/main/java/google/registry/tools/UpdateReservedListCommand.java
+++ b/core/src/main/java/google/registry/tools/UpdateReservedListCommand.java
@@ -62,10 +62,16 @@ final class UpdateReservedListCommand extends CreateOrUpdateReservedListCommand
     jpaTm()
         .transact(
             () -> {
-              checkArgument(
-                  ReservedListDao.checkExists(cloudSqlReservedList.getName()),
-                  "A reserved list of this name doesn't exist: %s.",
-                  cloudSqlReservedList.getName());
+              // This check is currently disabled because, during the Cloud SQL migration, we need
+              // to be able to update reserved lists in Datastore while simultaneously creating
+              // their first revision in Cloud SQL (i.e. if they haven't been migrated over yet).
+              // TODO(shicong): Re-instate this once all reserved lists are migrated to Cloud SQL,
+              //                 and add a unit test to verity that an exception will be thrown if
+              //                 the reserved list doesn't exist.
+              // checkArgument(
+              //     ReservedListDao.checkExists(cloudSqlReservedList.getName()),
+              //     "A reserved list of this name doesn't exist: %s.",
+              //     cloudSqlReservedList.getName());
               ReservedListDao.save(cloudSqlReservedList);
             });
   }
diff --git a/core/src/test/java/google/registry/tools/UpdateReservedListCommandTest.java b/core/src/test/java/google/registry/tools/UpdateReservedListCommandTest.java
index fc236fa72..f62c94c00 100644
--- a/core/src/test/java/google/registry/tools/UpdateReservedListCommandTest.java
+++ b/core/src/test/java/google/registry/tools/UpdateReservedListCommandTest.java
@@ -123,13 +123,14 @@ public class UpdateReservedListCommandTest extends
   }
 
   @Test
-  public void testSaveToCloudSql_noExceptionThrownWhenSaveFail() throws Exception {
-    // Note that, during the dual-write phase, we want to make sure that no exception will be
-    // thrown if saving reserved list to Cloud SQL fails.
+  public void testSaveToCloudSql_succeedsEvenPreviousListNotExist() throws Exception {
+    // Note that, during the dual-write phase, we just always save the revered list to
+    // Cloud SQL (if --also_cloud_sql is set) without checking if there is a list with
+    // same name. This is to backfill the existing list in Datastore when we update it.
     populateInitialReservedListInDatastore(true);
     runCommandForced(
         "--name=xn--q9jyb4c_common-reserved", "--input=" + reservedTermsPath, "--also_cloud_sql");
     verifyXnq9jyb4cInDatastore();
-    assertThat(ReservedListDao.checkExists("xn--q9jyb4c_common-reserved")).isFalse();
+    assertThat(ReservedListDao.checkExists("xn--q9jyb4c_common-reserved")).isTrue();
   }
 }