diff --git a/pubspec.yaml b/pubspec.yaml
index b77f03c..3cdda16 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -44,7 +44,7 @@ dependencies:
   meta: ^1.9.1
 
   # Protocol Buffers
-  protobuf: ^4.0.0
+  protobuf: ">=4.0.0 <7.0.0"
 
   # Web related libraries
   web: ^1.0.0