diff --git a/.gitignore b/.gitignore
index d87d4be..a7ad821 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,7 @@ spec/reports
 test/tmp
 test/version_tmp
 tmp
+
+# vim artifacts
+*.swp
+*.swo
diff --git a/README.md b/README.md
index 05f6c9b..bd09303 100644
--- a/README.md
+++ b/README.md
@@ -629,6 +629,25 @@ purposes; the exception is generated if `:retired_at` is set to _anything_.)
 You can retire events, categories, and entire versions; this system ensures the DSL continues to be a historical record
 of what things were in the past, as well as what they are today.
 
+### Requiring Properties
+
+Sometimes it is helpful to enforce the presence of certain properties. For example, imagine you are tracking views of
+a set of banners that advertise a set of new features. In order to determine which banners (and therefore features) are
+driving conversions, you need to be sure to include `:banner_id` and `:banner_size`. If there are many places in the
+code that can call this event, you may forget to pass along these properties. With `:required_properties` an exception
+is generated if the keys are not present _or if their values are blank_.
+
+```ruby
+global_events_prefix :ab
+
+version 1, "2014-02-04" do
+  category :user do
+    event :viewed_banner, "2014-02-04", "user creates a brand-new account", :required_properties => [ :banner_id, :banner_size ]
+  end
+end
+```
+
+
 ### Adding Notes to Events
 
 You can also add notes to events. They must be tagged with the author and the time, and they can be very useful for
diff --git a/lib/meta_events/definition/definition_set.rb b/lib/meta_events/definition/definition_set.rb
index b6c5583..b81a308 100644
--- a/lib/meta_events/definition/definition_set.rb
+++ b/lib/meta_events/definition/definition_set.rb
@@ -15,6 +15,7 @@ module Definition
     class DefinitionSet
       class BaseError < StandardError; end
       class RetiredEventError < BaseError; end
+      class RequiredPropertyMissingError < BaseError; end
 
       class << self
         # Creates an MetaEvents::Definition::DefinitionSet. +source+ can be one of:
diff --git a/lib/meta_events/definition/event.rb b/lib/meta_events/definition/event.rb
index 5eb72dc..10466b5 100644
--- a/lib/meta_events/definition/event.rb
+++ b/lib/meta_events/definition/event.rb
@@ -73,8 +73,10 @@ def initialize(category, name, *args, &block)
       # provide for required properties, property validation, or anything else.
       def validate!(properties)
         if retired_at
-          raise ::MetaEvents::Definition::DefinitionSet::RetiredEventError, "Event #{full_name} was retired at #{retired_at.inspect} (or its category or version was); you can't use it any longer."
+          raise ::MetaEvents::Definition::DefinitionSet::RetiredEventError,
+            "Event #{full_name} was retired at #{retired_at.inspect} (or its category or version was); you can't use it any longer."
         end
+        validate_properties!(properties)
       end
 
       # Returns, or sets, the description for an event.
@@ -142,10 +144,26 @@ def ensure_complete!
         raise ArgumentError, "You must record when you introduced event #{full_name}, either as an argument, in the options, or using 'introduced'" if (! @introduced)
       end
 
+      def validate_properties!(properties)
+        properties_with_indifferent_access = properties.with_indifferent_access
+        if @required_properties
+          missing_properties = [ ]
+          @required_properties.each do |required_property|
+            if properties_with_indifferent_access[required_property].blank?
+              missing_properties << required_property
+            end
+          end
+          unless missing_properties.empty?
+            raise ::MetaEvents::Definition::DefinitionSet::RequiredPropertyMissingError,
+              "Event #{full_name} requires the properties #{@required_properties.join(', ')}. #{missing_properties.join(', ')} were missing or had blank values."
+          end
+        end
+      end
+
       # Called with the set of options (which can be empty) supplied in the constructor; responsible for applying those
       # to the object properly.
       def apply_options!(options)
-        options.assert_valid_keys(:introduced, :desc, :description, :retired_at, :external_name)
+        options.assert_valid_keys(:introduced, :desc, :description, :retired_at, :external_name, :required_properties)
 
         introduced options[:introduced] if options[:introduced]
         desc options[:desc] if options[:desc]
@@ -153,6 +171,7 @@ def apply_options!(options)
         external_name options[:external_name] if options[:external_name]
 
         @retired_at = Time.parse(options[:retired_at]) if options[:retired_at]
+        @required_properties = Array(options[:required_properties]) if options[:required_properties]
       end
 
       # Called with the arguments (past the category and event name) supplied to the constructor; responsible for
diff --git a/meta_events.gemspec b/meta_events.gemspec
index 51508cc..2ec5e7f 100644
--- a/meta_events.gemspec
+++ b/meta_events.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "json", "~> 1.0"
   spec.add_dependency "activesupport", ">= 3.0"
 
-  spec.add_development_dependency "bundler", "~> 1.5"
+  spec.add_development_dependency "bundler", "~> 1.11.2"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec", "~> 2.14"
 end
diff --git a/spec/meta_events/definition/event_spec.rb b/spec/meta_events/definition/event_spec.rb
index 4336968..953d297 100644
--- a/spec/meta_events/definition/event_spec.rb
+++ b/spec/meta_events/definition/event_spec.rb
@@ -66,6 +66,14 @@
         allow(category).to receive(:retired_at).and_return(Time.parse("2013-02-01"))
         expect { instance.validate!(:foo => :bar) }.to raise_error(::MetaEvents::Definition::DefinitionSet::RetiredEventError, /2013/)
       end
+
+      it "should fail if required properties are missing" do
+        expect { klass.new(category, :foo, "2016-1-1", "foobar", :required_properties => [ :foo ]).validate!(:baz => :bar) }.to raise_error(::MetaEvents::Definition::DefinitionSet::RequiredPropertyMissingError, /foo/)
+      end
+
+      it "should fail if required properties have blank values" do
+        expect { klass.new(category, :foo, "2016-1-1", "foobar", :required_properties => [ :foo ]).validate!(:foo => '') }.to raise_error(::MetaEvents::Definition::DefinitionSet::RequiredPropertyMissingError, /foo/)
+      end
     end
 
     it "should return and allow setting its description via #desc" do
@@ -143,5 +151,15 @@
         expect(instance.external_name).to eq("my name")
       end
     end
+
+    context "with required properties" do
+      it "should work with strings and symbols" do
+        expect do
+          event = klass.new(category, :foo, "2016-1-1", "foobar", :required_properties => [ "string", :symbol ])
+          event.validate!('string' => "foo", :symbol => "foo")
+          event.validate!(:string => "foo", "symbol" => "foo")
+        end.to_not raise_error(::MetaEvents::Definition::DefinitionSet::RequiredPropertyMissingError)
+      end
+    end
   end
 end