diff --git a/lit-test/test/lit.cfg b/lit-test/test/lit.cfg
index 08f024e55..21b0acc09 100644
--- a/lit-test/test/lit.cfg
+++ b/lit-test/test/lit.cfg
@@ -1,3 +1,5 @@
+# -*- python -*-
+
 import os, subprocess
 import lit.util
 import lit.formats
@@ -10,8 +12,14 @@ config.suffixes = ['.py']
 
 python_executable = 'python3.5'
 
-harness = '{} {}'.format(python_executable, os.path.join(root, 'harness.py'))
-config.substitutions.append( ('%python', harness) )
+harness = os.path.join(root, 'harness.py')
+if os.getenv('COVERAGE'):
+    harness = 'coverage run --append --source=artiq {}'.format(harness)
+    config.environment['COVERAGE_FILE'] = os.path.join(root, '..', '.coverage')
+    config.substitutions.append( ('%python', harness) )
+else:
+    harness = '{} {}'.format(python_executable, harness)
+    config.substitutions.append( ('%python', harness) )
 
 not_ = '{} {}'.format(python_executable, os.path.join(root, 'not.py'))
 config.substitutions.append( ('%not', not_) )