diff --git a/Misc/NEWS b/Misc/NEWS
index a9f944a9b96..4dab25f056c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -22,6 +22,12 @@ Tests
 
 - Issue #20743: Fix a reference leak in test_tcl.
 
+Tools/Demos
+-----------
+
+- Issue #20535: PYTHONWARNING no longer affects the run_tests.py script.
+  Patch by Arfrever Frehtes Taifersar Arahesis.
+
 
 What's New in Python 3.4.0 release candidate 2?
 ===============================================
diff --git a/Tools/scripts/run_tests.py b/Tools/scripts/run_tests.py
index e2a20509781..a6c5da35e2f 100644
--- a/Tools/scripts/run_tests.py
+++ b/Tools/scripts/run_tests.py
@@ -32,6 +32,12 @@ def main(regrtest_args):
             ]
     # Allow user-specified interpreter options to override our defaults.
     args.extend(test.support.args_from_interpreter_flags())
+
+    # Workaround for issue #20355
+    os.environ.pop("PYTHONWARNINGS", None)
+    # Workaround for issue #20361
+    args.extend(['-W', 'error::BytesWarning'])
+
     args.extend(['-m', 'test',    # Run the test suite
                  '-r',            # Randomize test order
                  '-w',            # Re-run failed tests in verbose mode