diff --git a/tools/test-my-pr.py b/tools/test-my-pr.py
index a36af3c2f..4399193f5 100755
--- a/tools/test-my-pr.py
+++ b/tools/test-my-pr.py
@@ -188,7 +188,7 @@ if __name__ == "__main__":
             myfile.write(package + '\n')
             diff = lib.diff_results('main', results_to_diff[0], 'your', results_to_diff[1])
             if not main_crashed and not your_crashed and diff != '':
-                myfile.write('libraries:' + libraries +'\n')
+                myfile.write('libraries:' + ','.join(libraries) +'\n')
                 myfile.write('diff:\n' + diff + '\n')
 
         if not main_crashed and not your_crashed: