diff --git a/docsite/source/rules.html.md b/docsite/source/rules.html.md
index 33b8e3b1..77081856 100644
--- a/docsite/source/rules.html.md
+++ b/docsite/source/rules.html.md
@@ -181,6 +181,23 @@ contract.call(email: 'jane@doe.org', login: 'jane', password: "").errors.to_h
 # => {:password=>["password is required"]}
 ```
 
+The `key?` method supports passing an explicit key name for rules that have multiple keys.
+
+```ruby
+class DistanceContract < Dry::Validation::Contract
+  schema do
+    optional(:kilometers).filled(:integer)
+    optional(:miles).filled(:integer)
+  end
+
+  rule(:kilometers, :miles) do
+    if key?(:kilometers) ^ key?(:miles)
+      base.failure("must only contain one of: kilometers, miles")
+    end
+  end
+end
+```
+
 ### Checking for previous errors
 
 Sometimes you may be interested in adding an error when some other error has happened.
diff --git a/lib/dry/validation/evaluator.rb b/lib/dry/validation/evaluator.rb
index 31984053..ccaeb83b 100644
--- a/lib/dry/validation/evaluator.rb
+++ b/lib/dry/validation/evaluator.rb
@@ -155,16 +155,23 @@ def value
       #
       # This is useful when dealing with rules for optional keys
       #
-      # @example
+      # @example use the default key name
       #   rule(:age) do
       #     key.failure(:invalid) if key? && value < 18
       #   end
       #
+      # @example specify the key name
+      #   rule(:start_date, :end_date) do
+      #     if key?(:start_date) && !key?(:end_date)
+      #       key(:end_date).failure("must provide an end_date with start_date")
+      #     end
+      #   end
+      #
       # @return [Boolean]
       #
       # @api public
-      def key?
-        values.key?(key_name)
+      def key?(name = key_name)
+        values.key?(name)
       end
 
       # Check if there are any errors on the schema under the provided path
diff --git a/spec/integration/evaluator_spec.rb b/spec/integration/evaluator_spec.rb
index 32ccbca9..8b89d30c 100644
--- a/spec/integration/evaluator_spec.rb
+++ b/spec/integration/evaluator_spec.rb
@@ -12,7 +12,7 @@
   end
 
   let(:options) do
-    {keys: [:email], result: {}, values: values, _context: {}}
+    {keys: [:email, :name], result: {}, values: values, _context: {}}
   end
 
   let(:values) do
@@ -46,4 +46,20 @@
       end
     end
   end
+
+  describe "#key?" do
+    subject(:evaluator) do
+      Dry::Validation::Evaluator.new(contract, **options)
+    end
+
+    it "delegates to #values" do
+      expect(values).to receive(:key?).with(:name)
+      evaluator.key?(:name)
+    end
+
+    it "uses #key_name as the default argument" do
+      expect(values).to receive(:key?).with(:email)
+      evaluator.key?
+    end
+  end
 end