diff --git a/autotest/ogr/ogr_gpkg.py b/autotest/ogr/ogr_gpkg.py
index 2c76b25c2418..9b9b339f0195 100755
--- a/autotest/ogr/ogr_gpkg.py
+++ b/autotest/ogr/ogr_gpkg.py
@@ -7244,10 +7244,15 @@ def test_ogr_gpkg_background_rtree_build(filename):
     ds = gdaltest.gpkg_dr.CreateDataSource(filename)
     with gdaltest.config_option("OGR_GPKG_THREADED_RTREE_AT_FIRST_FEATURE", "YES"):
         lyr = ds.CreateLayer("foo")
+    assert lyr.StartTransaction() == ogr.OGRERR_NONE
     for i in range(1000):
         f = ogr.Feature(lyr.GetLayerDefn())
         f.SetGeometryDirectly(ogr.CreateGeometryFromWkt("POINT(%d %d)" % (i, i)))
         assert lyr.CreateFeature(f) == ogr.OGRERR_NONE
+        if i == 500:
+            assert lyr.CommitTransaction() == ogr.OGRERR_NONE
+            assert lyr.StartTransaction() == ogr.OGRERR_NONE
+    assert lyr.CommitTransaction() == ogr.OGRERR_NONE
     ds = None
     assert gdal.VSIStatL(filename + ".tmp_rtree_foo.db") is None
 
diff --git a/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp b/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
index 0e22866236b7..b23b98fb01c8 100644
--- a/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
+++ b/ogr/ogrsf_frmts/gpkg/ogrgeopackagetablelayer.cpp
@@ -2173,6 +2173,10 @@ OGRErr OGRGeoPackageTableLayer::CreateOrUpsertFeature( OGRFeature *poFeature, bo
             else if( !bUpsert && m_bAllowedRTreeThread && !m_bErrorDuringRTreeThread )
             {
                 GPKGRTreeEntry sEntry;
+#ifdef DEBUG_VERBOSE
+                if( m_aoRTreeEntries.empty() )
+                    CPLDebug("GPKG", "Starting to fill m_aoRTreeEntries at FID " CPL_FRMT_GIB, nFID);
+#endif
                 sEntry.nId = nFID;
                 sEntry.fMinX = rtreeValueDown(oEnv.MinX);
                 sEntry.fMaxX = rtreeValueUp(oEnv.MaxX);
@@ -2226,7 +2230,7 @@ void OGRGeoPackageTableLayer::SetDeferredSpatialIndexCreation( bool bFlag )
         // For unit tests
         if( CPLTestBool(CPLGetConfigOption("OGR_GPKG_THREADED_RTREE_AT_FIRST_FEATURE", "NO")) )
         {
-            m_nRTreeBatchSize = 1;
+            m_nRTreeBatchSize = 10;
             m_nRTreeBatchesBeforeStart = 1;
         }
     }
@@ -2363,11 +2367,21 @@ void OGRGeoPackageTableLayer::AsyncRTreeThreadFunction()
     }
 
     SQLCommand(m_hAsyncDBHandle, "BEGIN");
+    GIntBig nCount = 0;
     while( true )
     {
         const auto aoEntries = m_oQueueRTreeEntries.get_and_pop_front();
         if( aoEntries.empty() )
             break;
+#ifdef DEBUG_VERBOSE
+        CPLDebug("GPKG", "AsyncRTreeThreadFunction(): "
+                 "Processing batch of %d features, "
+                 "starting at FID " CPL_FRMT_GIB " and ending "
+                 "at FID " CPL_FRMT_GIB,
+                 static_cast<int>(aoEntries.size()),
+                 aoEntries.front().nId,
+                 aoEntries.back().nId);
+#endif
         for( const auto& entry: aoEntries )
         {
             if( (entry.nId % 500000) == 0 )
@@ -2382,6 +2396,7 @@ void OGRGeoPackageTableLayer::AsyncRTreeThreadFunction()
             }
             sqlite3_reset(hStmt);
 
+            nCount ++;
             sqlite3_bind_int64(hStmt,1,entry.nId);
             sqlite3_bind_double(hStmt,2,entry.fMinX);
             sqlite3_bind_double(hStmt,3,entry.fMaxX);
@@ -2408,6 +2423,7 @@ void OGRGeoPackageTableLayer::AsyncRTreeThreadFunction()
     }
 
     sqlite3_finalize(hStmt);
+    CPLDebug("GPKG", "AsyncRTreeThreadFunction(): " CPL_FRMT_GIB " rows inserted into RTree", nCount);
 
     if( m_bErrorDuringRTreeThread )
     {