diff --git a/lib/headers.ml b/lib/headers.ml
index 6c5320ca..ff6fce01 100644
--- a/lib/headers.ml
+++ b/lib/headers.ml
@@ -95,9 +95,9 @@ let replace t name value =
       if CI.equal needle name
       then (
         if seen
-        then loop t name nv true
-        else nv::loop t name nv true)
-      else nv'::loop t name nv seen
+        then loop t needle nv true
+        else nv::loop t needle nv true)
+      else nv'::loop t needle nv seen
   in
   try loop t name (name,value) false
   with Local -> t
diff --git a/lib_test/test_httpaf.ml b/lib_test/test_httpaf.ml
index 223e586c..333565b9 100644
--- a/lib_test/test_httpaf.ml
+++ b/lib_test/test_httpaf.ml
@@ -126,6 +126,13 @@ module Headers = struct
         "a"
         "d");
 
+    check "replace middle element"
+      ~expect:["e", "f"; "c", "z"; "a", "b"]
+      (Headers.replace
+         (Headers.of_list ["e", "f"; "c", "d"; "a", "b"])
+         "c"
+         "z");
+
     check "remove multiple trailing elements"
       ~expect:["c", "d"; "a", "d"]
       (Headers.replace
@@ -994,7 +1001,7 @@ module Client_connection = struct
   let tests =
     [ "GET"         , `Quick, test_get
     ; "Response EOF", `Quick, test_response_eof
-    ; "report_exn"  , `Quick, test_report_exn 
+    ; "report_exn"  , `Quick, test_report_exn
     ; "input_shrunk", `Quick, test_input_shrunk
     ]
 end