diff --git a/chrome/content/zotero/xpcom/connector/server_connector.js b/chrome/content/zotero/xpcom/connector/server_connector.js
index c80293b25a..68576ae7ce 100644
--- a/chrome/content/zotero/xpcom/connector/server_connector.js
+++ b/chrome/content/zotero/xpcom/connector/server_connector.js
@@ -1135,6 +1135,10 @@ Zotero.Server.Connector.Import.prototype = {
 	permitBookmarklet: false,
 	
 	init: async function (requestData) {
+		if (!('X-Zotero-Connector-API-Version' in requestData.headers)) {
+			return 400;
+		}
+		
 		let translate = new Zotero.Translate.Import();
 		translate.setString(requestData.data);
 		let translators = await translate.getTranslators();
diff --git a/test/tests/server_connectorTest.js b/test/tests/server_connectorTest.js
index 8a52c03df6..93a97205e8 100644
--- a/test/tests/server_connectorTest.js
+++ b/test/tests/server_connectorTest.js
@@ -1393,7 +1393,10 @@ describe("Connector Server", function () {
 				'POST',
 				endpoint,
 				{
-					headers: { "Content-Type": "text/plain" },
+					headers: {
+						"Content-Type": "text/plain",
+						"X-Zotero-Connector-API-Version": "2"
+					},
 					body: 'Owl'
 				}
 			));
@@ -1418,7 +1421,10 @@ describe("Connector Server", function () {
 				'POST',
 				endpoint,
 				{
-					headers: { "Content-Type": "application/x-bibtex" },
+					headers: {
+						"Content-Type": "application/x-bibtex",
+						"X-Zotero-Connector-API-Version": "2"
+					},
 					body: resource
 				}
 			);	
@@ -1451,7 +1457,10 @@ describe("Connector Server", function () {
 				'POST',
 				endpoint,
 				{
-					headers: { "Content-Type": "application/x-bibtex" },
+					headers: {
+						"Content-Type": "application/x-bibtex",
+						"X-Zotero-Connector-API-Version": "2"
+					},
 					body: resource,
 					successCodes: false
 				}