diff --git a/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
index 80df2fe1a1f..0cdf97465d0 100644
--- a/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
+++ b/src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc
@@ -235,7 +235,7 @@ static void alts_zero_copy_grpc_protector_destroy(
 
 static tsi_result alts_zero_copy_grpc_protector_max_frame_size(
     tsi_zero_copy_grpc_protector* self, size_t* max_frame_size) {
-  if (self == nullptr) return TSI_INVALID_ARGUMENT;
+  if (self == nullptr || max_frame_size == nullptr) return TSI_INVALID_ARGUMENT;
   alts_zero_copy_grpc_protector* protector =
       reinterpret_cast<alts_zero_copy_grpc_protector*>(self);
   *max_frame_size = protector->max_protected_frame_size;
diff --git a/src/core/tsi/transport_security_grpc.cc b/src/core/tsi/transport_security_grpc.cc
index 69591d7343a..cec872690de 100644
--- a/src/core/tsi/transport_security_grpc.cc
+++ b/src/core/tsi/transport_security_grpc.cc
@@ -67,7 +67,7 @@ void tsi_zero_copy_grpc_protector_destroy(tsi_zero_copy_grpc_protector* self) {
 
 tsi_result tsi_zero_copy_grpc_protector_max_frame_size(
     tsi_zero_copy_grpc_protector* self, size_t* max_frame_size) {
-  if (self == nullptr) return TSI_INVALID_ARGUMENT;
+  if (self == nullptr || max_frame_size == nullptr) return TSI_INVALID_ARGUMENT;
   if (self->vtable->max_frame_size == nullptr) return TSI_UNIMPLEMENTED;
   return self->vtable->max_frame_size(self, max_frame_size);
 }