diff --git a/api/src/org/labkey/api/migration/DefaultMigrationSchemaHandler.java b/api/src/org/labkey/api/migration/DefaultMigrationSchemaHandler.java
index 019d5f6e30d..08f4fcd3c2c 100644
--- a/api/src/org/labkey/api/migration/DefaultMigrationSchemaHandler.java
+++ b/api/src/org/labkey/api/migration/DefaultMigrationSchemaHandler.java
@@ -290,7 +290,7 @@ public static void logUnseenAttachmentTypes()
         Set<AttachmentType> unseen = new HashSet<>(AttachmentService.get().getAttachmentTypes());
         unseen.removeAll(SEEN);
 
-        if (SEEN.isEmpty())
+        if (unseen.isEmpty())
             DatabaseMigrationService.LOG.info("All AttachmentTypes have been seen");
         else
             DatabaseMigrationService.LOG.info("These AttachmentTypes have not been seen: {}", unseen.stream().map(type -> type.getClass().getSimpleName()).collect(Collectors.joining(", ")));
diff --git a/assay/src/org/labkey/assay/AssayResultMigrationSchemaHandler.java b/assay/src/org/labkey/assay/AssayResultMigrationSchemaHandler.java
index 16e0a57ad82..da9a0a794c2 100644
--- a/assay/src/org/labkey/assay/AssayResultMigrationSchemaHandler.java
+++ b/assay/src/org/labkey/assay/AssayResultMigrationSchemaHandler.java
@@ -12,18 +12,15 @@
 import org.labkey.api.data.SimpleFilter.SQLClause;
 import org.labkey.api.data.SqlSelector;
 import org.labkey.api.data.TableInfo;
-import org.labkey.api.data.TableSelector;
 import org.labkey.api.migration.AssaySkipContainers;
 import org.labkey.api.migration.DatabaseMigrationService.DataFilter;
 import org.labkey.api.migration.DefaultMigrationSchemaHandler;
 import org.labkey.api.migration.ExperimentDeleteService;
 import org.labkey.api.util.GUID;
-import org.labkey.api.util.StringUtilsLabKey;
 import org.labkey.api.util.logging.LogHelper;
 import org.labkey.assay.plate.PlateReplicateStatsDomainKind;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Set;
 
 class AssayResultMigrationSchemaHandler extends DefaultMigrationSchemaHandler
@@ -38,7 +35,7 @@ public AssayResultMigrationSchemaHandler()
     private boolean skipTable(TableInfo sourceTable)
     {
         // For now, we're ignoring this table since it's empty in our first migration client's database
-        return Strings.CI.endsWith(sourceTable.getName(), PlateReplicateStatsDomainKind.ASSAY_PLATE_REPLICATE);
+        return Strings.CI.endsWith(sourceTable.getName(), PlateReplicateStatsDomainKind.NAME);
     }
 
     @Override
@@ -63,8 +60,8 @@ public FilterClause getContainerClause(TableInfo sourceTable, Set<GUID> containe
     @Override
     public void addDomainDataFilterClause(OrClause orClause, DataFilter filter, TableInfo sourceTable, Set<String> selectColumnNames)
     {
-        // No filtering on assay results for now; just add the passed in containers. Note that these will be filtered
-        // if AssaySkipContainers is configured.
+        // No row-by-row filtering on assay results for now; just add the passed in containers. Note that these will be
+        // filtered by container if AssaySkipContainers is configured.
         orClause.addClause(getContainerClause(sourceTable, filter.containers()));
     }
 
@@ -92,9 +89,6 @@ public void afterTable(TableInfo sourceTable, TableInfo targetTable, SimpleFilte
                 // Delete exp.Data, exp.Object, etc. rows associated with the rows that weren't copied
                 ExperimentDeleteService.get().deleteDataRows(notCopiedObjectIds);
             }
-
-            // TODO: Temp!
-            LOG.info("   " + StringUtilsLabKey.pluralize(new TableSelector(sourceTable, Collections.singleton("DataId")).stream(Integer.class).distinct().count(), "distinct DataId"));
         }
     }
 }
diff --git a/experiment/src/org/labkey/experiment/DataClassMigrationSchemaHandler.java b/experiment/src/org/labkey/experiment/DataClassMigrationSchemaHandler.java
index 45232046c93..2e93cba7b5d 100644
--- a/experiment/src/org/labkey/experiment/DataClassMigrationSchemaHandler.java
+++ b/experiment/src/org/labkey/experiment/DataClassMigrationSchemaHandler.java
@@ -90,14 +90,18 @@ public void addDomainDataFilterClause(OrClause orClause, DataFilter filter, Tabl
     @Override
     public void afterTable(TableInfo sourceTable, TableInfo targetTable, SimpleFilter notCopiedFilter)
     {
-        // Select all ObjectIds associated with the not-copied rows from the source database. Our notCopiedFilter
-        // works on the data class provisioned table, so we need to use a sub-select (as opposed to a join) to avoid
-        // ambiguous column references.
-        SQLFragment objectIdSql = new SQLFragment("SELECT ObjectId FROM exp.Object WHERE ObjectURI IN (SELECT LSID FROM ")
-            .appendIdentifier(sourceTable.getSelectName())
-            .append(" ")
-            .append(notCopiedFilter.getSQLFragment(sourceTable.getSqlDialect()))
-            .append(")");
+        // Select LSIDs from the just-copied rows in the target table
+        Collection<String> copiedLsids = new TableSelector(targetTable, Collections.singleton("LSID")).getCollection(String.class);
+
+        // Select all ObjectIds associated with the not-copied rows from the source database
+        SQLFragment objectIdSql = new SQLFragment("SELECT ObjectId FROM exp.Data d INNER JOIN ")
+                .appendIdentifier(sourceTable.getSelectName())
+                .append(" dc ON d.LSID = dc.LSID");
+
+        // Don't create an empty IN clause; need to work around issue where "NOT xxx IN (NULL)" evaluates to NULL.
+        if (!copiedLsids.isEmpty())
+            objectIdSql.append(" AND NOT dc.LSID").appendInClause(copiedLsids, sourceTable.getSqlDialect());
+
         Collection<Long> notCopiedObjectIds = new SqlSelector(sourceTable.getSchema(), objectIdSql).getCollection(Long.class);
 
         if (notCopiedObjectIds.isEmpty())