diff --git a/src/header/map.rs b/src/header/map.rs
index ab3afc47..1eab5bf6 100644
--- a/src/header/map.rs
+++ b/src/header/map.rs
@@ -1855,7 +1855,7 @@ where
     type Error = Error;
 
     fn try_from(c: &'a HashMap<K, V>) -> Result<Self, Self::Error> {
-        c.into_iter()
+        c.iter()
             .map(|(k, v)| -> crate::Result<(HeaderName, T)> {
                 let name = TryFrom::try_from(k).map_err(Into::into)?;
                 let value = TryFrom::try_from(v).map_err(Into::into)?;