1 files changed, 1 insertions, 1 deletions
diff --git a/src/ser.rs b/src/ser.rs
index b5b19ed..c3b93d6 100644
--- a/src/ser.rs
+++ b/src/ser.rs
@@ -48,7 +48,7 @@ impl ConfigSerializer {
             self.keys
                 .get_mut(len - 1)
                 .map(|pair| pair.1 = pair.1.map(|i| i + 1).or(Some(0)))
-                .ok_or(ConfigError::Message(format!(
+                .ok_or_else(|| ConfigError::Message(format!(
                     "last key is not found in {} keys",
                     len
                 )))