diff --git a/reframe/core/modules.py b/reframe/core/modules.py
index d29a47aff..e8c9c504b 100644
--- a/reframe/core/modules.py
+++ b/reframe/core/modules.py
@@ -8,6 +8,7 @@
 #
 
 import abc
+import functools
 import os
 import re
 from collections import OrderedDict
@@ -1030,6 +1031,7 @@ def available_modules(self, substr):
 
         return ret
 
+    @functools.lru_cache(maxsize=128)
     def conflicted_modules(self, module):
         if module.collection:
             # Conflicts have no meaning in module collection. The modules