diff --git a/src/qr.rs b/src/qr.rs
index be627e0..d133c9e 100644
--- a/src/qr.rs
+++ b/src/qr.rs
@@ -151,7 +151,7 @@ impl QRCode {
     ) -> Result<Self, QRCodeError> {
         use crate::placement::create_matrix;
 
-        let mode = mode.unwrap_or(encode::best_encoding(input));
+        let mode = mode.unwrap_or_else(|| encode::best_encoding(input));
         let level = ecl.unwrap_or(ECL::Q);
 
         let version = match Version::get(mode, level, input.len()) {