diff --git a/requirements.txt b/requirements.txt
index 0036049..9de21be 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -23,7 +23,7 @@ lazy-object-proxy==1.4.3
 MarkupSafe==1.1.1
 mccabe==0.6.1
 nexmo==2.4.0
-protobuf==3.11.3
+protobuf==3.15.0
 pyasn1==0.4.8
 pyasn1-modules==0.2.8
 pycparser==2.19