diff --git a/triggers/http_response.go b/triggers/http_response.go
index 8975fce80..def4221ee 100644
--- a/triggers/http_response.go
+++ b/triggers/http_response.go
@@ -49,7 +49,7 @@ func FromTriggerResponse(triggerResponse *pb.TriggerResponse) (*HttpResponse, er
 
 		if httpContext.GetHeaders() != nil {
 			for key, val := range httpContext.GetHeaders() {
-				fasthttpHeader.Add(key, val)
+				fasthttpHeader.Set(key, val)
 			}
 		}
 
diff --git a/worker/faas_worker.go b/worker/faas_worker.go
index 28ea4dd96..a9f44ee94 100644
--- a/worker/faas_worker.go
+++ b/worker/faas_worker.go
@@ -122,7 +122,7 @@ func (s *FaasWorker) HandleHttpRequest(trigger *triggers.HttpRequest) (*triggers
 	fasthttpHeader := &fasthttp.ResponseHeader{}
 
 	for key, val := range httpResponse.GetHeaders() {
-		fasthttpHeader.Add(key, val)
+		fasthttpHeader.Set(key, val)
 	}
 
 	response := &triggers.HttpResponse{
diff --git a/worker/http_worker.go b/worker/http_worker.go
index e599315dd..b96eda060 100644
--- a/worker/http_worker.go
+++ b/worker/http_worker.go
@@ -67,7 +67,7 @@ func (h *HttpWorker) HandleHttpRequest(trigger *triggers.HttpRequest) (*triggers
 	}
 
 	for key, val := range trigger.Header {
-		httpRequest.Header.Add(key, val)
+		httpRequest.Header.Set(key, val)
 	}
 
 	httpRequest.Header.Del("Content-Length")