diff --git a/python/lib/dependabot/python/file_parser/pyproject_files_parser.rb b/python/lib/dependabot/python/file_parser/pyproject_files_parser.rb
index db0c77f3ea8..6ce7ef57e8f 100644
--- a/python/lib/dependabot/python/file_parser/pyproject_files_parser.rb
+++ b/python/lib/dependabot/python/file_parser/pyproject_files_parser.rb
@@ -27,7 +27,7 @@ def dependency_set
           dependency_set = Dependabot::FileParsers::Base::DependencySet.new
 
           dependency_set += pyproject_dependencies if using_poetry? || using_pep621?
-          dependency_set += lockfile_dependencies if lockfile
+          dependency_set += lockfile_dependencies if using_poetry? && lockfile
 
           dependency_set
         end
diff --git a/python/spec/dependabot/python/file_parser/pyproject_files_parser_spec.rb b/python/spec/dependabot/python/file_parser/pyproject_files_parser_spec.rb
index 0b1caa68ff2..f3f85f7d8b6 100644
--- a/python/spec/dependabot/python/file_parser/pyproject_files_parser_spec.rb
+++ b/python/spec/dependabot/python/file_parser/pyproject_files_parser_spec.rb
@@ -311,6 +311,23 @@
       subject(:dependencies) { parser.dependency_set.dependencies }
 
       its(:length) { is_expected.to eq(0) }
+
+      context "and a leftover poetry.lock" do
+        let(:poetry_lock) do
+          Dependabot::DependencyFile.new(
+            name: "poetry.lock",
+            content: poetry_lock_body
+          )
+        end
+        let(:poetry_lock_body) do
+          fixture("poetry_locks", poetry_lock_fixture_name)
+        end
+        let(:poetry_lock_fixture_name) { "poetry.lock" }
+
+        let(:files) { [pyproject, pdm_lock, poetry_lock] }
+
+        its(:length) { is_expected.to eq(0) }
+      end
     end
 
     context "with optional dependencies" do