diff --git a/operators/cuda/mul_sigmoid.h b/operators/cuda/mul_sigmoid.h
index 1eb8f2702..a6ddcb74d 100644
--- a/operators/cuda/mul_sigmoid.h
+++ b/operators/cuda/mul_sigmoid.h
@@ -10,6 +10,8 @@ namespace contrib {
 
 /**
 * MulSigmoid(X) = X * Sigmoid(X)
+
+No shape broadcasting supported.
 */
 template <typename T>
 struct MulSigmoid {
@@ -36,6 +38,8 @@ struct MulSigmoid {
 
 /**
 * MulSigmoid(X, Y) = X * Y * Sigmoid(Y)
+
+No shape broadcasting supported.
 */
 template <typename T>
 struct MulMulSigmoid {
@@ -65,4 +69,4 @@ struct MulMulSigmoid {
   }
 };
 
-}  // namespace contrib
\ No newline at end of file
+}  // namespace contrib