diff --git a/lib/data_mapper/validation/rule/numericalness.rb b/lib/data_mapper/validation/rule/numericalness.rb
index 414e5c68..f69ac62a 100644
--- a/lib/data_mapper/validation/rule/numericalness.rb
+++ b/lib/data_mapper/validation/rule/numericalness.rb
@@ -28,6 +28,7 @@ def self.rules_for(attribute_name, options)
           lte = scour_options_of_keys(options, [:lte, :less_than_or_equal_to])
           eq  = scour_options_of_keys(options, [:eq,  :equal, :equals, :exactly, :equal_to])
           ne  = scour_options_of_keys(options, [:ne,  :not_equal_to])
+    
 
           rules = []
           rules << Integer.new(attribute_name, options)                                    if int
@@ -58,8 +59,11 @@ def valid?(resource)
           #   if so, return a dummy validator when expected is nil
           return true if expected.nil?
 
-          value = resource.validation_property_value(attribute_name)
+          # Expected could be a Proc.
+          @expected = expected.call(resource) if expected.is_a?(Proc)
 
+          value = resource.validation_property_value(attribute_name)
+          
           optional?(value) || valid_numericalness?(value)
         end
 
diff --git a/spec/fixtures/trip.rb b/spec/fixtures/trip.rb
new file mode 100644
index 00000000..c7fe1d24
--- /dev/null
+++ b/spec/fixtures/trip.rb
@@ -0,0 +1,48 @@
+
+# -*- coding: utf-8 -*-
+
+module DataMapper
+  module Validation
+    module Fixtures
+      class Trip
+        #
+        # Behaviors
+        #
+
+        include DataMapper::Resource
+
+        #
+        # Properties
+        #
+
+        property :id,     Serial
+
+        without_auto_validations do
+          property :adults,   Integer
+          property :infants,  Integer
+          property :children, Integer
+        end
+
+        #
+        # Validations
+        #
+        validates_numericality_of :adults, :gt => Proc.new { |s| s.min_adults }, :lt => Proc.new { |s| s.max_adults } 
+        validates_numericality_of :children, :gte => Proc.new { |s| s.adults }
+        validates_numericality_of :infants, :lte => Proc.new { |s| s.adults }
+        
+        def min_adults; 0; end
+        def max_adults; 4; end
+
+        def self.valid_instance(overrides = {})
+          defaults = {
+            :adults                    => 2,
+            :children                  => 3,
+            :infants                   => 2
+          }
+
+          new(defaults.merge(overrides))
+        end
+      end
+    end # Fixtures
+  end # Validations
+end # DataMapper
diff --git a/spec/integration/numeric_validator/gt_with_proc_spec.rb b/spec/integration/numeric_validator/gt_with_proc_spec.rb
new file mode 100644
index 00000000..b5d7c75d
--- /dev/null
+++ b/spec/integration/numeric_validator/gt_with_proc_spec.rb
@@ -0,0 +1,27 @@
+
+require 'spec_helper'
+require 'integration/numeric_validator/spec_helper'
+
+describe 'DataMapper::Validations::Fixtures::Trip' do
+  before :all do
+    DataMapper::Validations::Fixtures::Trip.auto_migrate!
+    @model = DataMapper::Validations::Fixtures::Trip.valid_instance
+    @model.valid?
+  end
+
+  it_should_behave_like "valid model"
+
+
+  describe "when adults less than #min_adults" do
+    before :all do
+      @model.adults = 0 
+      @model.valid?
+    end
+
+    it_should_behave_like "invalid model"
+  
+    it 'has a meaningful error message' do
+      @model.errors.on(:adults).should == ["Adults must be greater than #{@model.min_adults}"]
+    end
+  end
+end
diff --git a/spec/integration/numeric_validator/gte_with_proc_spec.rb b/spec/integration/numeric_validator/gte_with_proc_spec.rb
new file mode 100644
index 00000000..69581145
--- /dev/null
+++ b/spec/integration/numeric_validator/gte_with_proc_spec.rb
@@ -0,0 +1,28 @@
+
+
+require 'spec_helper'
+require 'integration/numeric_validator/spec_helper'
+
+describe 'DataMapper::Validations::Fixtures::Trip' do
+  before :all do
+    DataMapper::Validations::Fixtures::Trip.auto_migrate!
+    @model = DataMapper::Validations::Fixtures::Trip.valid_instance
+    @model.valid?
+  end
+
+  it_should_behave_like "valid model"
+
+
+  describe "when child count less than adults" do
+    before :all do
+      @model.children = 1
+      @model.valid?
+    end
+
+    it_should_behave_like "invalid model"
+  
+    it 'has a meaningful error message' do
+      @model.errors.on(:children).should == ["Children must be greater than or equal to #{@model.adults}"]
+    end
+  end
+end
diff --git a/spec/integration/numeric_validator/lt_with_proc_spec.rb b/spec/integration/numeric_validator/lt_with_proc_spec.rb
new file mode 100644
index 00000000..f3b92b3c
--- /dev/null
+++ b/spec/integration/numeric_validator/lt_with_proc_spec.rb
@@ -0,0 +1,28 @@
+
+
+require 'spec_helper'
+require 'integration/numeric_validator/spec_helper'
+
+describe 'DataMapper::Validations::Fixtures::Trip' do
+  before :all do
+    DataMapper::Validations::Fixtures::Trip.auto_migrate!
+    @model = DataMapper::Validations::Fixtures::Trip.valid_instance
+    @model.valid?
+  end
+
+  it_should_behave_like "valid model"
+
+
+  describe "when adults greater than #max_adults" do
+    before :all do
+      @model.adults = 5
+      @model.valid?
+    end
+
+    it_should_behave_like "invalid model"
+  
+    it 'has a meaningful error message' do
+      @model.errors.on(:adults).should == ["Adults must be less than #{@model.max_adults}"]
+    end
+  end
+end
diff --git a/spec/integration/numeric_validator/lte_with_proc_spec.rb b/spec/integration/numeric_validator/lte_with_proc_spec.rb
new file mode 100644
index 00000000..007f0f29
--- /dev/null
+++ b/spec/integration/numeric_validator/lte_with_proc_spec.rb
@@ -0,0 +1,29 @@
+
+
+
+require 'spec_helper'
+require 'integration/numeric_validator/spec_helper'
+
+describe 'DataMapper::Validations::Fixtures::Trip' do
+  before :all do
+    DataMapper::Validations::Fixtures::Trip.auto_migrate!
+    @model = DataMapper::Validations::Fixtures::Trip.valid_instance
+    @model.valid?
+  end
+
+  it_should_behave_like "valid model"
+
+
+  describe "when infants greater than #adults" do
+    before :all do
+      @model.infants = 3
+      @model.valid?
+    end
+
+    it_should_behave_like "invalid model"
+  
+    it 'has a meaningful error message' do
+      @model.errors.on(:infants).should == ["Infants must be less than or equal to #{@model.adults}"]
+    end
+  end
+end