diff --git a/test/qpy_compat/run_tests.sh b/test/qpy_compat/run_tests.sh
index a6ff67b14a94..f1c770809c77 100755
--- a/test/qpy_compat/run_tests.sh
+++ b/test/qpy_compat/run_tests.sh
@@ -42,7 +42,7 @@ python -m venv "$qiskit_venv"
 "$qiskit_venv/bin/pip" install -c "$repo_root/constraints.txt" "$qiskit_dev_wheel" packaging
 
 # Run all of the tests of cross-Qiskit-version compatibility.
-"$qiskit_python" "$our_dir/get_versions.py" | parallel --colsep=" " bash "$our_dir/process_version.sh" -p "$qiskit_python"
+"$qiskit_python" "$our_dir/get_versions.py" | parallel -j 2 --colsep=" " bash "$our_dir/process_version.sh" -p "$qiskit_python"
 
 # Test dev compatibility with itself.
 dev_version="$("$qiskit_python" -c 'import qiskit; print(qiskit.__version__)')"