diff --git a/src/ChangeLog b/src/ChangeLog
index dec3d4ca..57644018 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2005-04-15  Hrvoje Niksic  <hniksic@xemacs.org>
+
+	* ptimer.c: Use _POSIX_TIMERS - 0 > 0, which handles the case when
+	_POSIX_TIMERS is defined but empty, as well as the case when it is
+	undefined.  Do the same with the check for _POSIX_MONOTONIC_CLOCK.
+	Suggested by Larry Jones.
+
 2005-04-15  Hrvoje Niksic  <hniksic@xemacs.org>
 
 	* ptimer.c: Check that _POSIX_TIMERS is defined as well as > 0.
diff --git a/src/ptimer.c b/src/ptimer.c
index 3a09ceba..3eeb78c6 100644
--- a/src/ptimer.c
+++ b/src/ptimer.c
@@ -92,7 +92,7 @@ extern int errno;
 #if defined(WINDOWS) || defined(__CYGWIN__)
 # define PTIMER_WINDOWS		/* use Windows timers */
 #else
-# if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
+# if _POSIX_TIMERS - 0 > 0
 #  define PTIMER_POSIX		/* use POSIX timers (clock_gettime) */
 # else
 #  ifdef HAVE_GETTIMEOFDAY
@@ -139,7 +139,7 @@ posix_init (void)
     int id;
     int sysconf_name;
   } clocks[] = {
-#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
+#if _POSIX_MONOTONIC_CLOCK - 0 >= 0
     { CLOCK_MONOTONIC, _SC_MONOTONIC_CLOCK },
 #endif
 #ifdef CLOCK_HIGHRES