diff --git a/changelog.markdown b/changelog.markdown
index 0a77639..6522980 100644
--- a/changelog.markdown
+++ b/changelog.markdown
@@ -5,6 +5,7 @@
 - **Breaking change:** the `@` operator used for retrieving request parameters now automatically decodes special characters using `decodeUrl`.
 - Fix for [#211](https://github.com/dom96/jester/issues/211) - custom routers now have the same error handling as normal routes.
 - Fix for [#269](https://github.com/dom96/jester/issues/269) - a bug that prevented redirecting from within error handlers.
+- The `resp` (taking a HTTP code, headers and content) now correctly handles headers with duplicate keys.
 
 ## 0.5.0 - 17/10/2020
 
diff --git a/jester.nim b/jester.nim
index 9cebf8e..48c49a1 100644
--- a/jester.nim
+++ b/jester.nim
@@ -543,6 +543,7 @@ proc serve*(
 
 template setHeader*(headers: var ResponseHeaders, key, value: string): typed =
   ## Sets a response header using the given key and value.
+  ##
   ## Overwrites if the header key already exists.
   bind isNone
   if isNone(headers):
@@ -560,6 +561,17 @@ template setHeader*(headers: var ResponseHeaders, key, value: string): typed =
       # Add key if it doesn't exist.
       headers = some(h & @({key: value}))
 
+template addHeader*(headers: var ResponseHeaders, key, value: string): typed =
+  ## Adds a response header using the given key and value.
+  ##
+  ## If a header of the same `key` already exists then it is kept,
+  ## the specified value is added and the original isn't overwritten.
+  bind isNone
+  if isNone(headers):
+    headers = some(@({key: value}))
+  else:
+    headers = some(h & @({key: value}))
+
 template resp*(code: HttpCode,
                headers: openarray[tuple[key, val: string]],
                content: string): typed =
@@ -567,7 +579,7 @@ template resp*(code: HttpCode,
   bind TCActionSend
   result = (TCActionSend, code, none[RawHeaders](), content, true)
   for header in headers:
-    setHeader(result[2], header[0], header[1])
+    addHeader(result[2], header[0], header[1])
   break route
 
 
@@ -1406,7 +1418,7 @@ proc routesEx(name: string, body: NimNode): NimNode =
       let `matchProcVarIdent`: MatchProcSync = `matchIdent`
       let `errorProcVarIdent`: ErrorProc = `errorHandlerIdent`
       let `pairIdent`: MatchPairSync = (`matchProcVarIdent`, `errorProcVarIdent`)
-  
+
 
   # TODO: Replace `body`, `headers`, `code` in routes with `result[i]` to
   # get these shortcuts back without sacrificing usability.