diff --git a/CMakeLists.txt b/CMakeLists.txt
index 39cd7ef..6029243 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 
-cmake_minimum_required(VERSION 2.8)
+cmake_minimum_required(VERSION 3.5)
 project(termistor)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
diff --git a/libtsm/src/shared/shl-pty.c b/libtsm/src/shared/shl-pty.c
index 5dfe977..96c769c 100644
--- a/libtsm/src/shared/shl-pty.c
+++ b/libtsm/src/shared/shl-pty.c
@@ -9,6 +9,8 @@
  * PTY Helpers
  */
 
+#define _GNU_SOURCE
+
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
@@ -146,7 +148,7 @@ static int pty_init_child(int fd)
 	if (r < 0)
 		return -errno;
 
-	for (i = 1; i < SIGUNUSED; ++i)
+	for (i = 1; i < SIGSYS; ++i)
 		signal(i, SIG_DFL);
 
 	r = grantpt(fd);