diff --git a/src/cache.cpp b/src/cache.cpp
index c049b7f..cb0a2d0 100644
--- a/src/cache.cpp
+++ b/src/cache.cpp
@@ -46,6 +46,9 @@ using namespace std;
 //-------------------------------------------------------------------
 // Utility
 //-------------------------------------------------------------------
+#ifndef CLOCK_REALTIME
+#define CLOCK_REALTIME          0
+#endif
 #ifndef CLOCK_MONOTONIC
 #define CLOCK_MONOTONIC         CLOCK_REALTIME
 #endif