diff --git a/ev.c b/ev.c
index 1a4e5f1..24d00d0 100644
--- a/ev.c
+++ b/ev.c
@@ -282,9 +282,11 @@ typedef ev_watcher *W;
 typedef ev_watcher_list *WL;
 typedef ev_watcher_time *WT;
 
+#if EV_USE_MONOTONIC
 /* sig_atomic_t is used to avoid per-thread variables or locking but still */
 /* giving it a reasonably high chance of working on typical architetcures */
 static sig_atomic_t have_monotonic; /* did clock_gettime (CLOCK_MONOTONIC) work? */
+#endif
 
 #ifdef _WIN32
 # include "ev_win32.c"