diff --git a/src/main/java/swurg/workers/Worker.java b/src/main/java/swurg/workers/Worker.java
index f5edcd1..6789671 100644
--- a/src/main/java/swurg/workers/Worker.java
+++ b/src/main/java/swurg/workers/Worker.java
@@ -166,7 +166,7 @@ private List<HttpParameter> buildHttpRequestParameters(List<Parameter> parameter
           Schema schema = parameter.getSchema();
           String value = Optional.ofNullable(schema)
               .map(Schema::getType)
-              .orElse(null);
+              .orElse("");
 
           if ("header".equals(in))
             httpParameters.add(HttpParameter.cookieParameter(name, value));
@@ -195,4 +195,4 @@ else if ("query".equals(in))
 
     return httpParameters;
   }
-}
\ No newline at end of file
+}