diff --git a/tpl/macros_struct.twig b/tpl/macros_struct.twig
index 4cf61d0..4b45f11 100644
--- a/tpl/macros_struct.twig
+++ b/tpl/macros_struct.twig
@@ -225,7 +225,9 @@ func Save{{ ctx.s.name }}CollectionDiff(ctx context.Context, dbe metadb.Execer,
 		}
 
 		key := rec.changedFields.GetFieldsKey()
-		if _, ok := byFieldsKey[key]; !ok {
+		_, ok := byFieldsKey[key]
+		firstRecord := !ok
+		if firstRecord {
 			builder := NewQueryDiffBuilder()
 
 			builder.query.WriteString("INSERT INTO `{{ ctx.table_name }}` ({{ ctx.pkey_column_expr }}")
@@ -263,13 +265,11 @@ func Save{{ ctx.s.name }}CollectionDiff(ctx context.Context, dbe metadb.Execer,
 		{% if has_token(ctx.s, 'table_json_kv') %}
 		var jsonBuilder strings.Builder
 
-		jsonValues := make([]any, 0, {{ ctx.json_fields|length }})
 		{% for f in ctx.json_fields %}
 		{% set fname = f|fname %}
 		if rec.{{ f|fname }}Changed() {
 			{%~ if f.type is builtin %}
-			jsonBuilder.WriteString(",'$.{{ f|alias }}',?")
-			jsonValues = append(jsonValues, rec.{{ f|fname }})
+			jsonBuilder.WriteString(",'$.{{ f|alias }}',JSON_EXTRACT(VALUES(`kv`), '$.{{ f|alias }}')")
 			{%~ else %}
 			jsonBuilder.WriteString(",'$.{{ f|alias }}',")
 			jsonBytes, err := json.Marshal(rec.{{ fname }})
@@ -284,15 +284,17 @@ func Save{{ ctx.s.name }}CollectionDiff(ctx context.Context, dbe metadb.Execer,
 		{% endfor %}
 
 		if jsonBuilder.Len() > 0 {
-			builder.query.WriteString(",`kv`")
+			if firstRecord {
+				builder.query.WriteString(",`kv`")
+
+				builder.update.WriteString(",`kv`=JSON_SET(`kv`")
+				builder.update.WriteString(jsonBuilder.String())
+				builder.update.WriteRune(')')
+			}
+
 			builder.values.WriteString(",?")
 
-			builder.update.WriteString(",`kv`=JSON_SET(`kv`")
-			builder.update.WriteString(jsonBuilder.String())
-			builder.update.WriteRune(')')
-
 			builder.rawValues = append(builder.rawValues, rec.{{ ctx.s.name }}JsonValues)
-			builder.rawValues = append(builder.rawValues, jsonValues...)
 		}
 		{% endif %}