1 files changed, 5 insertions, 1 deletions
diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index 3c80d584fe..4e9a305d9d 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -76,7 +76,11 @@ module ActiveModel
           elsif observer.respond_to?(:instance)
             observer.instance
           else
-            raise ArgumentError, "#{observer} must be a lowercase, underscored class name (or an instance of the class itself) responding to the instance method. Example: Person.observers = :big_brother # calls BigBrother.instance"
+            raise ArgumentError,
+              "#{observer} must be a lowercase, underscored class name (or an " +
+              "instance of the class itself) responding to the instance " +
+              "method. Example: Person.observers = :big_brother # calls " +
+              "BigBrother.instance"
           end
         end