configure: fix HAVE_CLOCK_MONOTONIC spelling
diff --git a/configure.ac b/configure.ac
index 296132c..634d635 100755
--- a/configure.ac
+++ b/configure.ac
@@ -1356,7 +1356,7 @@
 dnl --------------------------------------
 AC_CHECK_DECL(CLOCK_MONOTONIC,
 	[AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS -lrt"])
-	 AC_DEFINE(HAVE_MONOTONIC_CLOCK,, Have monotonic clock)
+	 AC_DEFINE(HAVE_CLOCK_MONOTONIC,, Have monotonic clock)
 ], [AC_MSG_RESULT(no)], [QUAGGA_INCLUDES])
 
 dnl -------------------