diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index 108cf29c0a8..43d8c64da0b 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -1349,9 +1349,10 @@ argp.add_argument(
     choices=[
         'default', 'gcc4.4', 'gcc4.6', 'gcc4.8', 'gcc4.9', 'gcc5.3', 'gcc7.2',
         'gcc_musl', 'clang3.4', 'clang3.5', 'clang3.6', 'clang3.7', 'clang7.0',
-        'python2.7', 'python3.4', 'python3.5', 'python3.6', 'python3.7', 'python3.8', 'pypy',
-        'pypy3', 'python_alpine', 'all_the_cpythons', 'electron1.3',
-        'electron1.6', 'coreclr', 'cmake', 'cmake_vs2015', 'cmake_vs2017'
+        'python2.7', 'python3.4', 'python3.5', 'python3.6', 'python3.7',
+        'python3.8', 'pypy', 'pypy3', 'python_alpine', 'all_the_cpythons',
+        'electron1.3', 'electron1.6', 'coreclr', 'cmake', 'cmake_vs2015',
+        'cmake_vs2017'
     ],
     default='default',
     help=