diff --git a/include/common/compat.h b/include/common/compat.h
index e0f00dc..9b97d82 100644
--- a/include/common/compat.h
+++ b/include/common/compat.h
@@ -104,10 +104,17 @@
 #define F_SETPIPE_SZ (1024 + 7)
 #endif
 
-/* systems without such defines do not know clockid_t */
+/* systems without such defines do not know clockid_t or timer_t */
 #if !(_POSIX_TIMERS > 0) || (_POSIX_C_SOURCE < 199309L)
 #undef clockid_t
 #define clockid_t empty_t
+#undef timer_t
+#define timer_t empty_t
+#endif
+
+/* define a dummy value to designate "no timer". Use only 32 bits. */
+#ifndef TIMER_INVALID
+#define TIMER_INVALID ((timer_t)(unsigned long)(0xfffffffful))
 #endif
 
 #if defined(TPROXY) && defined(NETFILTER)
diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 3209909..268dd63 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -58,6 +58,7 @@
 
 extern struct thread_info {
 	clockid_t clock_id;
+	timer_t wd_timer;          /* valid timer or TIMER_INVALID if not set */
 	uint64_t prev_cpu_time;    /* previous per thread CPU time */
 	uint64_t prev_mono_time;   /* previous system wide monotonic time  */
 	unsigned int idle_pct;     /* idle to total ratio over last sample (percent) */
@@ -407,6 +408,7 @@
 extern struct thread_info {
 	pthread_t pthread;
 	clockid_t clock_id;
+	timer_t wd_timer;          /* valid timer or TIMER_INVALID if not set */
 	uint64_t prev_cpu_time;    /* previous per thread CPU time */
 	uint64_t prev_mono_time;   /* previous system wide monotonic time  */
 	unsigned int idle_pct;     /* idle to total ratio over last sample (percent) */