diff --git a/ortools/sat/cp_model.proto b/ortools/sat/cp_model.proto
index 06abe9eb94..d69fc8e43d 100644
--- a/ortools/sat/cp_model.proto
+++ b/ortools/sat/cp_model.proto
@@ -78,7 +78,7 @@ message IntegerArgumentProto {
 
 message LinearExpressionProto {
   repeated int32 vars = 1;
-  repeated int32 coeffs = 2;
+  repeated int64 coeffs = 2;
   int64 offset = 3;
 }