diff --git a/requirements/multiple_category_classification_keras.txt b/requirements/multiple_category_classification_keras.txt
index df32bde..cb7b035 100644
--- a/requirements/multiple_category_classification_keras.txt
+++ b/requirements/multiple_category_classification_keras.txt
@@ -52,7 +52,7 @@ pexpect==4.7.0
 pickleshare==0.7.5
 prometheus-client==0.7.1
 prompt-toolkit==2.0.9
-protobuf==3.9.1
+protobuf==3.15.0
 ptyprocess==0.6.0
 Pygments==2.4.2
 pyparsing==2.4.2