diff --git a/lib/middleware.js b/lib/middleware.js
index 4a64297..827b053 100644
--- a/lib/middleware.js
+++ b/lib/middleware.js
@@ -57,7 +57,7 @@ Middleware.prototype._createStream = function() {
 Middleware.prototype._validateMessageSignature = function(messageValidatorService) {
 	const self = this;
 	this._app.use((request, response, next) => {
-		const serverSideSignature = request.headers.X_Viber_Content_Signature || request.query.sig;
+		const serverSideSignature = request.headers['x-viber-content-signature'] || request.query.sig;
 		if (!messageValidatorService.validateMessage(serverSideSignature, request.body)) {
 			self._logger.warn("Could not validate message signature", serverSideSignature);
 			return;
@@ -66,4 +66,4 @@ Middleware.prototype._validateMessageSignature = function(messageValidatorServic
 	});
 };
 
-module.exports = Middleware;
\ No newline at end of file
+module.exports = Middleware;