diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -598,6 +598,8 @@ def tsttest(test, wd, options, replaceme
     f.close()
 
     script = []
+    if options.debug:
+        script.append('set -x\n')
     if os.getenv('MSYSTEM'):
         script.append('alias pwd="pwd -W"\n')
     for n, l in enumerate(t):