diff --git a/rswag-specs/lib/rswag/specs/example_group_helpers.rb b/rswag-specs/lib/rswag/specs/example_group_helpers.rb
index 93f1050..c293c63 100644
--- a/rswag-specs/lib/rswag/specs/example_group_helpers.rb
+++ b/rswag-specs/lib/rswag/specs/example_group_helpers.rb
@@ -36,7 +36,9 @@ module Rswag
       end
 
       def parameter(attributes)
-        attributes[:required] = true if attributes[:in].to_sym == :path
+        if attributes[:in] && attributes[:in].to_sym == :path
+          attributes[:required] = true
+        end
 
         if metadata.has_key?(:operation)
           metadata[:operation][:parameters] ||= []
diff --git a/rswag-specs/spec/rswag/specs/example_group_helpers_spec.rb b/rswag-specs/spec/rswag/specs/example_group_helpers_spec.rb
index 96d08b0..619a8d7 100644
--- a/rswag-specs/spec/rswag/specs/example_group_helpers_spec.rb
+++ b/rswag-specs/spec/rswag/specs/example_group_helpers_spec.rb
@@ -120,6 +120,15 @@ module Rswag
             )
           end
         end
+
+        context "when 'in' parameter key is not defined" do
+          before { subject.parameter(name: :id) }
+          let(:api_metadata) { { operation: {} } }
+
+          it "does not require the 'in' parameter key" do
+            expect(api_metadata[:operation][:parameters]).to match([ name: :id ])
+          end
+        end
       end
 
       describe '#response(code, description)' do