diff --git a/src/transaction.rs b/src/transaction.rs
index 6e174b6..a55e1c4 100644
--- a/src/transaction.rs
+++ b/src/transaction.rs
@@ -421,7 +421,7 @@ impl<'tx> Transaction<'tx> {
 
             sw = response.status_words().code();
 
-            if 0 != out_data.len() && (out_data.len() - response.data().len() > max_out) {
+            if !out_data.is_empty() && (out_data.len() - response.data().len() > max_out) {
                 error!(
                     "output buffer too small: wanted to write {}, max was {}",
                     out_data.len() - response.data().len(),