diff --git a/graphgen/models/generator/masked_fill_in_blank_generator.py b/graphgen/models/generator/masked_fill_in_blank_generator.py
index bc6f06c8..355cadcf 100644
--- a/graphgen/models/generator/masked_fill_in_blank_generator.py
+++ b/graphgen/models/generator/masked_fill_in_blank_generator.py
@@ -115,7 +115,7 @@ async def generate(
         match = re.search(mask_pattern, context)
         if match:
             gth = match.group(0)
-            masked_context = mask_pattern.sub("___", context)
+            masked_context = mask_pattern.sub("{ }", context)
         else:
             logger.debug(
                 "Regex Match Failed!\n"