diff --git a/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile b/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile
index 1d23f77fdf3..cd469423dd4 100644
--- a/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile
+++ b/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile
@@ -17,6 +17,11 @@ gem 'mutex_m', '~> 0.2.0'
 gem 'base64', '~> 0.1.0'
 gem 'bigdecimal', '~> 1.2', '>= 1.2.7'
 
+# i18n >= 1.15.0 uses the Fiber[] API (Ruby 3.2+) and breaks on Ruby 3.1.
+# Keep it on the 1.14 series so the deployment-mode build (bundle lock --update)
+# cannot resolve an i18n version incompatible with the Ruby 3.1 runtime.
+gem 'i18n', '~> 1.14.0'
+
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem "tzinfo-data", platforms: %i[ mingw mswin x64_mingw jruby ]
 
diff --git a/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile.lock b/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile.lock
index fa63e29ed8c..495993280d7 100644
--- a/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile.lock
+++ b/lib-injection/build/docker/ruby/lib_injection_rails_app/Gemfile.lock
@@ -76,7 +76,7 @@ GEM
     erubi (1.12.0)
     globalid (1.1.0)
       activesupport (>= 5.0)
-    i18n (1.12.0)
+    i18n (1.14.7)
       concurrent-ruby (~> 1.0)
     io-console (0.6.0)
     irb (1.6.2)
@@ -170,6 +170,7 @@ PLATFORMS
 
 DEPENDENCIES
   debug
+  i18n (~> 1.14.0)
   puma (~> 5.0)
   rails (~> 7.0.3)
   sprockets-rails