diff --git a/tests/run-tests b/tests/run-tests
index da18c6c765..9e94026fa2 100755
--- a/tests/run-tests
+++ b/tests/run-tests
@@ -10,10 +10,10 @@ from glob import glob
 # to the correct executable.
 if os.name == 'nt':
     CPYTHON3 = os.getenv('MICROPY_CPYTHON3', 'python3.exe')
-    MP_PY = '../windows/micropython.exe'
+    MICROPYTHON = os.getenv('MICROPY_MICROPYTHON', '../windows/micropython.exe')
 else:
     CPYTHON3 = os.getenv('MICROPY_CPYTHON3', 'python3')
-    MP_PY = '../unix/micropython'
+    MICROPYTHON = os.getenv('MICROPY_MICROPYTHON', '../unix/micropython')
 
 # Set of tests that we shouldn't run under Travis CI
 skip_travis_tests = set(['basics/memoryerror.py'])
@@ -40,7 +40,7 @@ if test_on_pyboard:
     pyb = pyboard.Pyboard('/dev/ttyACM0')
     pyb.enter_raw_repl()
 
-running_under_travis = os.environ.get('TRAVIS', 'false') == 'true'
+running_under_travis = os.getenv('TRAVIS') == 'true'
 
 for test_file in tests:
     if running_under_travis and test_file in skip_travis_tests:
@@ -62,7 +62,7 @@ for test_file in tests:
             output_mupy = b'CRASH'
     else:
         try:
-            output_mupy = subprocess.check_output([MP_PY, '-X', 'emit=bytecode', test_file])
+            output_mupy = subprocess.check_output([MICROPYTHON, '-X', 'emit=bytecode', test_file])
         except subprocess.CalledProcessError:
             output_mupy = b'CRASH'