diff --git a/adapters/klab.adapter.copernicus/src/main/java/org/integratedmodelling/adapter/copernicus/datacubes/CopernicusCDSDatacube.java b/adapters/klab.adapter.copernicus/src/main/java/org/integratedmodelling/adapter/copernicus/datacubes/CopernicusCDSDatacube.java
index 5de52572e..fec039c02 100644
--- a/adapters/klab.adapter.copernicus/src/main/java/org/integratedmodelling/adapter/copernicus/datacubes/CopernicusCDSDatacube.java
+++ b/adapters/klab.adapter.copernicus/src/main/java/org/integratedmodelling/adapter/copernicus/datacubes/CopernicusCDSDatacube.java
@@ -145,7 +145,10 @@ protected boolean downloadChunk(int chunk, String variable, File destinationDire
 		String endpoint = getEndpointUrl("/processes/" + this.dataset + "/execute");
 		Logging.INSTANCE.info("Ask for job id: " + endpoint + " with key " + apiKey + "\n" + jsonBody);
 		HttpResponse<JsonNode> response = Unirest.post(endpoint)
-				.header(CDS_API_KEY_HEADER, apiKey).header("Accept", "application/json").body(jsonBody).asJson();
+				.header(CDS_API_KEY_HEADER, apiKey)
+				.header("Content-Type", "application/json")
+				.header("Accept", "application/json")
+				.body(jsonBody).asJson();
 
 		if (response.isSuccess()) {