diff --git a/test/runner/requirements/constraints.txt b/test/runner/requirements/constraints.txt
index 44e022f9985..65aa61914ed 100644
--- a/test/runner/requirements/constraints.txt
+++ b/test/runner/requirements/constraints.txt
@@ -22,3 +22,4 @@ voluptuous >= 0.11.0 # Schema recursion via Self
 virtualenv < 16.0.0 ; python_version < '2.7' # virtualenv 16.0.0 and later require python 2.7 or later
 pyopenssl < 18.0.0 ; python_version < '2.7' # pyOpenSSL 18.0.0 and later require python 2.7 or later
 pyfmg == 0.6.1 # newer versions do not pass current unit tests
+pycparser < 2.19 ; python_version < '2.7' # pycparser 2.19 and later require python 2.7 or later