diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2dbebc6..271aa61 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## 1.2.4
+
+### Fixed
+
+- Fixed issue with `sync_all!` finding obsolete classes that are no longer defined as support tables in development or test environments.
+
 ## 1.2.3
 
 ### Fixed
diff --git a/VERSION b/VERSION
index 0495c4a..e8ea05d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.2.3
+1.2.4
diff --git a/lib/support_table_data.rb b/lib/support_table_data.rb
index 022a65f..400d471 100644
--- a/lib/support_table_data.rb
+++ b/lib/support_table_data.rb
@@ -380,6 +380,7 @@ def support_table_classes(*extra_classes)
       active_record_classes = ActiveRecord::Base.descendants.reject { |klass| klass.name.nil? }
       active_record_classes.sort_by(&:name).each do |klass|
         next unless klass.include?(SupportTableData)
+        next unless klass.instance_variable_defined?(:@support_table_data_files) && klass.instance_variable_get(:@support_table_data_files).is_a?(Array)
         next if klass.abstract_class?
         next if classes.include?(klass)
         classes << klass