diff --git a/configure.ac b/configure.ac
index e705ba1..f720c7c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,6 +12,7 @@
 AC_PROG_MAKE_SET
 
 # Checks for libraries.
+PKG_CHECK_MODULES([SYSTEMD], [libsystemd > 221])
 
 # Checks for header files.