diff --git a/public/class-jwt-auth-public.php b/public/class-jwt-auth-public.php
index 430ecaa..68e6df5 100644
--- a/public/class-jwt-auth-public.php
+++ b/public/class-jwt-auth-public.php
@@ -219,10 +219,10 @@ public function determine_current_user( $user ) {
 		/**
 		 * We still need to get the Authorization header and check for the token.
 		 */
-		$auth_header = $_SERVER['HTTP_AUTHORIZATION'] ? sanitize_text_field( $_SERVER['HTTP_AUTHORIZATION'] ) : false;
+		$auth_header = ! empty( $_SERVER['HTTP_AUTHORIZATION'] ) ? sanitize_text_field( $_SERVER['HTTP_AUTHORIZATION'] ) : false;
 		/* Double check for different auth header string (server dependent) */
 		if ( ! $auth_header ) {
-			$auth_header = $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ? sanitize_text_field( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) : false;
+			$auth_header = ! empty( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) ? sanitize_text_field( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) : false;
 		}
 
 		if ( ! $auth_header ) {