diff --git a/Gemfile b/Gemfile
index 6654b285a72..95d65ec30c7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -309,7 +309,7 @@ group :development do
   gem 'foreman', '~> 0.84.0'
   gem 'brakeman', '~> 4.2', require: false
 
-  gem 'letter_opener_web', '~> 1.3.0'
+  gem 'letter_opener_web', '~> 1.3.4'
   gem 'rblineprof', '~> 0.3.6', platform: :mri, require: false
 
   # Better errors handler
diff --git a/Gemfile.lock b/Gemfile.lock
index ceece1da8d7..c08f0c24ba6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -444,9 +444,9 @@ GEM
       rest-client (~> 2.0)
     launchy (2.4.3)
       addressable (~> 2.3)
-    letter_opener (1.4.1)
+    letter_opener (1.7.0)
       launchy (~> 2.2)
-    letter_opener_web (1.3.0)
+    letter_opener_web (1.3.4)
       actionmailer (>= 3.2)
       letter_opener (~> 1.0)
       railties (>= 3.2)
@@ -1093,7 +1093,7 @@ DEPENDENCIES
   kaminari (~> 1.0)
   knapsack (~> 1.17)
   kubeclient (~> 4.2.2)
-  letter_opener_web (~> 1.3.0)
+  letter_opener_web (~> 1.3.4)
   license_finder (~> 5.4)
   licensee (~> 8.9)
   lograge (~> 0.5)
diff --git a/changelogs/unreleased/pl-upgrade-letter_opener_web.yml b/changelogs/unreleased/pl-upgrade-letter_opener_web.yml
new file mode 100644
index 00000000000..9891344215a
--- /dev/null
+++ b/changelogs/unreleased/pl-upgrade-letter_opener_web.yml
@@ -0,0 +1,5 @@
+---
+title: Upgrade letter_opener_web to support Rails 5.1
+merge_request: 27829
+author:
+type: fixed