diff --git a/util/generate_build_files.py b/util/generate_build_files.py
index 0554b14..1d56059 100644
--- a/util/generate_build_files.py
+++ b/util/generate_build_files.py
@@ -250,13 +250,22 @@
         name_counts[name] = name_counts.get(name, 0) + 1
 
       first = True
+      test_names = set()
       for test in files['tests']:
         name = os.path.basename(test[0])
         if name_counts[name] > 1:
-          if '/' in test[1]:
-            name += '_' + os.path.splitext(os.path.basename(test[1]))[0]
+          if '/' in test[-1]:
+            arg = test[-1].replace('crypto/cipher/test/','')  # boooring
+            arg = arg.replace('/', '_')
+            arg = os.path.splitext(arg)[0]  # remove .txt
+            arg = arg.replace('_tests', '')
+            name += '_' + arg
           else:
-            name += '_' + test[1].replace('-', '_')
+            name += '_' + test[-1].replace('-', '_')
+
+        if name in test_names:
+          raise ValueError("test name %s is not unique" % name)
+        test_names.add(name)
 
         if not first:
           out.write('\n')