diff --git a/examples/research_projects/pplm/requirements.txt b/examples/research_projects/pplm/requirements.txt
index 70530cd7998..f93fde0f78f 100644
--- a/examples/research_projects/pplm/requirements.txt
+++ b/examples/research_projects/pplm/requirements.txt
@@ -19,4 +19,4 @@ pytest
 conllu
 sentencepiece != 0.1.92
 protobuf
-transformers==3.5.1
+transformers==4.38.0