diff --git a/configure.ac b/configure.ac
index c546a169..f34d433c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -153,6 +153,8 @@ AC_C_BIGENDIAN
 
 dnl Checks for functions and headers
 
+AC_CHECK_FUNC(clock_gettime, , [AC_CHECK_LIB(rt, clock_gettime)])
+
 AC_CHECK_FUNCS([SecureZeroMemory])
 
 dnl Switches.
diff --git a/src/curvecp/libcurvecp/nanoseconds.c b/src/curvecp/libcurvecp/nanoseconds.c
index de5309d5..65e6d9f8 100644
--- a/src/curvecp/libcurvecp/nanoseconds.c
+++ b/src/curvecp/libcurvecp/nanoseconds.c
@@ -7,7 +7,7 @@
 
 long long nanoseconds(void)
 {
-#ifdef CLOCK_REALTIME
+#if defined(CLOCK_REALTIME) && defined(HAVE_CLOCK_GETTIME)
   struct timespec t;
   if (clock_gettime(CLOCK_REALTIME,&t) != 0) return -1;
   return t.tv_sec * 1000000000LL + t.tv_nsec;