diff --git a/config/initializers/05-null_db_fallback.rb b/config/initializers/04-null_db_fallback.rb
similarity index 100%
rename from config/initializers/05-null_db_fallback.rb
rename to config/initializers/04-null_db_fallback.rb
diff --git a/config/initializers/05-check_db_encoding.rb b/config/initializers/05-check_db_encoding.rb
new file mode 100644
index 000000000000..afe594300cbe
--- /dev/null
+++ b/config/initializers/05-check_db_encoding.rb
@@ -0,0 +1,49 @@
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+icu_incompatible_encodings = %w[
+  EUC_JIS_2004
+  LATIN10
+  MULE_INTERNAL
+  SQL_ASCII
+  WIN874
+]
+
+database_encoding = ActiveRecord::Base.connection.select_value("SHOW SERVER_ENCODING")
+
+if database_encoding.in?(icu_incompatible_encodings)
+  abort <<~ERROR
+    INCOMPATIBLE DATABASE ENCODING DETECTED
+
+    Your database encoding is #{database_encoding}, which is incompatible with ICU
+    collation used in OpenProject v15.
+
+    Please check the instructions on how to change database encoding:
+    https://www.openproject.org/docs/installation-and-operations/misc/changing-database-encoding/
+  ERROR
+end