diff --git a/xmodule/conditional_block.py b/xmodule/conditional_block.py
index fbc2944dfc..4caed0f17d 100644
--- a/xmodule/conditional_block.py
+++ b/xmodule/conditional_block.py
@@ -326,7 +326,7 @@ class ConditionalBlock(
         descriptors = []
         for location in self.sources_list:
             try:
-                descriptor = self.system.get_block(location)
+                descriptor = self.runtime.get_block(location)
                 descriptors.append(descriptor)
             except ItemNotFoundError:
                 msg = "Invalid module by location."