diff --git a/spec/integration/rack/v2/headers_spec.rb b/spec/integration/rack/v2/headers_spec.rb
index abf3e3bba1..63c8e45727 100644
--- a/spec/integration/rack/v2/headers_spec.rb
+++ b/spec/integration/rack/v2/headers_spec.rb
@@ -1,6 +1,11 @@
 # frozen_string_literal: true
 
 describe Grape::Http::Headers do
+  it { expect(described_class::ALLOW).to eq('Allow') }
+  it { expect(described_class::CACHE_CONTROL).to eq('Cache-Control') }
+  it { expect(described_class::CONTENT_LENGTH).to eq('Content-Length') }
   it { expect(described_class::CONTENT_TYPE).to eq('Content-Type') }
+  it { expect(described_class::LOCATION).to eq('Location') }
+  it { expect(described_class::TRANSFER_ENCODING).to eq('Transfer-Encoding') }
   it { expect(described_class::X_CASCADE).to eq('X-Cascade') }
 end
diff --git a/spec/integration/rack/v3/headers_spec.rb b/spec/integration/rack/v3/headers_spec.rb
index 6d0de82c49..3f5375e0c7 100644
--- a/spec/integration/rack/v3/headers_spec.rb
+++ b/spec/integration/rack/v3/headers_spec.rb
@@ -1,6 +1,11 @@
 # frozen_string_literal: true
 
 describe Grape::Http::Headers do
+  it { expect(described_class::ALLOW).to eq('allow') }
+  it { expect(described_class::CACHE_CONTROL).to eq('cache-control') }
+  it { expect(described_class::CONTENT_LENGTH).to eq('content-length') }
   it { expect(described_class::CONTENT_TYPE).to eq('content-type') }
+  it { expect(described_class::LOCATION).to eq('location') }
+  it { expect(described_class::TRANSFER_ENCODING).to eq('transfer-encoding') }
   it { expect(described_class::X_CASCADE).to eq('x-cascade') }
 end