2 files changed, 22 insertions, 9 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 7eb008fc27..d97d4c7ed0 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -107,6 +107,21 @@ module ActiveRecord
     end
   end
 
+  class AmbiguousSourceReflectionForThroughAssociation < ActiveRecordError # :nodoc:
+    def initialize(klass, macro, association_name, options, possible_sources)
+      example_options = options.dup
+      example_options[:source] = possible_sources.first
+
+      super("Ambiguous source reflection for through association. Please " \
+            "specify a :source directive on your declaration like:\n" \
+            "\n" \
+            "  class #{klass} < ActiveRecord::Base\n" \
+            "    #{macro} :#{association_name}, #{example_options}\n" \
+            "  end"
+           )
+    end
+  end
+
   class HasManyThroughCantAssociateThroughHasOneOrManyReflection < ThroughCantAssociateThroughHasOneOrManyReflection #:nodoc:
   end
 
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index e1a3c59f08..f3e81ee1e2 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -878,15 +878,13 @@ module ActiveRecord
         }
 
         if names.length > 1
-          example_options = options.dup
-          example_options[:source] = source_reflection_names.first
-          ActiveSupport::Deprecation.warn \
-            "Ambiguous source reflection for through association. Please " \
-            "specify a :source directive on your declaration like:\n" \
-            "\n" \
-            "  class #{active_record.name} < ActiveRecord::Base\n" \
-            "    #{macro} :#{name}, #{example_options}\n" \
-            "  end"
+          raise AmbiguousSourceReflectionForThroughAssociation.new(
+            active_record.name,
+            macro,
+            name,
+            options,
+            source_reflection_names
+          )
         end
 
         @source_reflection_name = names.first