diff --git a/m4/clock_gettime b/m4/clock_gettime
index aa9542c5ec..9f872a8f1c 100644
--- a/m4/clock_gettime
+++ b/m4/clock_gettime
@@ -17,6 +17,7 @@ AC_DEFUN([AC_CLOCK],
   if test "$have_clock_gettime" = "no"; then
     AC_MSG_CHECKING([for clock_gettime in -lrt])
 
+    SAVED_LIBS=$LIBS
     LIBS="$LIBS -lrt"
 
     AC_TRY_LINK([ #include <time.h> ], [struct timespec ts; clock_gettime(CLOCK_MONOTONIC, &ts);], [
@@ -68,8 +69,9 @@ AC_DEFUN([AC_CLOCK],
   if test "$have_clock_get_time" = "yes"; then
     AC_DEFINE([HAVE_CLOCK_GET_TIME], 1, [do we have clock_get_time?])
   fi
-  RT_LIBS=LIBS
+  RT_LIBS=$LIBS
   AC_SUBST(RT_LIBS)
+  SAVED_LIBS=$LIBS
 ])
 
 dnl Local Variables: