diff --git a/configure.ac b/configure.ac
index c8174de3..7510f239 100644
--- a/configure.ac
+++ b/configure.ac
@@ -55,12 +55,12 @@ PKG_CHECK_MODULES(XFT, [xft])
 AC_SUBST(XFT_CFLAGS)
 AC_SUBST(XFT_LIBS)
 
-PKG_CHECK_MODULES(LIBSN, [libstartup-notification-1.0])
-AC_SUBST(LIBSN_CFLAGS)
-AC_SUBST(LIBSN_LIBS)
-if test "$LIBSN_LIBS"; then
-   AC_DEFINE(USE_LIBSN)
-fi
+PKG_CHECK_MODULES(LIBSN, [libstartup-notification-1.0],
+  AC_DEFINE(USE_LIBSN)
+  AC_SUBST(LIBSN_CFLAGS)
+  AC_SUBST(LIBSN_LIBS)
+  ,
+)
 
 # Check for X11 extensions
 X11_EXT_XKB