diff --git a/src/server/WFServer.cc b/src/server/WFServer.cc
index f314f2db..0bcc9e44 100644
--- a/src/server/WFServer.cc
+++ b/src/server/WFServer.cc
@@ -50,7 +50,7 @@ private:
 	std::atomic<size_t> *conn_count;
 };
 
-long WFServerBase::ssl_ctx_callback(SSL *ssl, int *al, void *arg)
+int WFServerBase::ssl_ctx_callback(SSL *ssl, int *al, void *arg)
 {
 	WFServerBase *server = (WFServerBase *)arg;
 	const char *servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
diff --git a/src/server/WFServer.h b/src/server/WFServer.h
index 7439f8b3..e9f8d65a 100644
--- a/src/server/WFServer.h
+++ b/src/server/WFServer.h
@@ -176,7 +176,7 @@ private:
 	int init(const struct sockaddr *bind_addr, socklen_t addrlen,
 			 const char *cert_file, const char *key_file);
 	int init_ssl_ctx(const char *cert_file, const char *key_file);
-	static long ssl_ctx_callback(SSL *ssl, int *al, void *arg);
+	static int ssl_ctx_callback(SSL *ssl, int *al, void *arg);
 	virtual int create_listen_fd();
 	virtual void handle_unbound();