diff --git a/src/runtime/darwin-os.c b/src/runtime/darwin-os.c
index c0dce91..412a1e6 100644
--- a/src/runtime/darwin-os.c
+++ b/src/runtime/darwin-os.c
@@ -32,6 +32,10 @@
 #include <time.h>
 #include <sys/syscall.h>
 
+#if __MAC_OS_X_VERSION_MIN_REQUIRED < 101200
+#include <sys/resource.h>
+#endif
+
 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 #include <libkern/OSAtomic.h>
 #endif
@@ -368,3 +372,39 @@ sb_nanosleep(time_t sec, int nsec) {
         }
     }
 }
+
+#if __MAC_OS_X_VERSION_MIN_REQUIRED < 101200
+
+int clock_gettime (int clock_id, struct timespec *ts)
+{
+    int returnValue = -1;
+
+    if (clock_id == CLOCK_MONOTONIC || clock_id == CLOCK_REALTIME) {
+        clock_serv_t cclock;
+        mach_timespec_t mts;
+
+        host_get_clock_service(mach_host_self(), REALTIME_CLOCK, &cclock);
+        if (clock_get_time(cclock, &mts) == 0) {
+            mach_port_deallocate(mach_task_self(), cclock);
+            ts->tv_sec = mts.tv_sec;
+            ts->tv_nsec = mts.tv_nsec;
+
+            returnValue = 0;
+        }
+
+    } else if (clock_id == CLOCK_PROCESS_CPUTIME_ID) {
+        struct rusage usage;
+
+        if (getrusage(RUSAGE_SELF, &usage) == 0) {
+            ts->tv_sec = usage.ru_utime.tv_sec + usage.ru_stime.tv_sec;
+            ts->tv_nsec = (usage.ru_utime.tv_usec + usage.ru_stime.tv_usec) *
+                1000;
+
+            returnValue = 0;
+        }
+    }
+
+    return returnValue;
+}
+
+#endif
diff --git a/src/runtime/darwin-os.h b/src/runtime/darwin-os.h
index ac7b9ac..18839b2 100644
--- a/src/runtime/darwin-os.h
+++ b/src/runtime/darwin-os.h
@@ -42,4 +42,12 @@ void darwin_init(void);
 typedef dispatch_semaphore_t os_sem_t;
 #endif
 
+#if __MAC_OS_X_VERSION_MIN_REQUIRED < 101200
+
+#define CLOCK_REALTIME 0
+#define CLOCK_MONOTONIC 6
+#define CLOCK_PROCESS_CPUTIME_ID 12
+
+#endif
+
 #endif /* _DARWIN_OS_H */