diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index f807a8fe16bdc329ae5d792fdf2b293d58c80e3b..85f202b823cd02dab5df9fba4631abfd5425d908 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -515,11 +515,17 @@ def add_route(mapping, path_ast, name, anchor)
         named_routes[name] = route if name
 
         if route.segment_keys.include?(:controller)
-          ActiveSupport::Deprecation.warn("Using a dynamic :controller segment in a route is deprecated and will be remove in Rails 5.1")
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :controller segment in a route is deprecated and
+            will be removed in Rails 5.1
+          MSG
         end
 
         if route.segment_keys.include?(:action)
-          ActiveSupport::Deprecation.warn("Using a dynamic :action segment in a route is deprecated and will be remove in Rails 5.1")
+          ActiveSupport::Deprecation.warn(<<-MSG.squish)
+            Using a dynamic :action segment in a route is deprecated and
+            will be removed in Rails 5.1
+          MSG
         end
 
         route