diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index 0073c6ba26fc6d448abe680a63b945aa4906ea87..fc6a3cdee891446d978d8a3a8561f4ab7fb49d0e 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -53,8 +53,9 @@ def initialize(*args)
 
     def create_root
       self.destination_root = File.expand_path(app_path, destination_root)
-      empty_directory '.'
+      valid_app_const?
 
+      empty_directory '.'
       set_default_accessors!
       FileUtils.cd(destination_root)
     end
@@ -193,7 +194,14 @@ def app_name
       end
 
       def app_const
-        @app_const ||= "#{app_name.classify}::Application"
+        @app_const ||= "#{app_name.gsub(/\W/, '_').squeeze('_').classify}::Application"
+      end
+
+      def valid_app_const?
+        case app_const
+        when /^\d/
+          raise Error, "Invalid application name #{app_name}. Please give a name which does not start with numbers."
+        end
       end
 
       def app_secret
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 2cba42551e501dce10daad386970ad37b6e9a62d..235da530f9f8e1f6ae1dba1d696f5f4b24d6c946 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -53,6 +53,16 @@ def test_invalid_database_option_raises_an_error
     assert_match /Invalid value for \-\-database option/, content
   end
 
+  def test_invalid_application_name_raises_an_error
+    content = capture(:stderr){ Rails::Generators::AppGenerator.start [File.join(destination_root, "43-things")] }
+    assert_equal "Invalid application name 43-things. Please give a name which does not start with numbers.\n", content
+  end
+
+  def test_invalid_application_name_is_fixed
+    silence(:stdout){ Rails::Generators::AppGenerator.start [File.join(destination_root, "things-43")] }
+    assert_file "things-43/config/environment.rb", /Things43::Application/
+  end
+
   def test_config_database_is_added_by_default
     run_generator
     assert_file "config/database.yml", /sqlite3/