diff --git a/cpu-all.h b/cpu-all.h
index 1a6a812259..ebe8bfbadb 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -1021,7 +1021,7 @@ static inline int64_t cpu_get_real_ticks (void)
 
 static inline int64_t cpu_get_real_ticks(void)
 {
-#if __mips_isa_rev >= 2
+#if defined(__mips_isa_rev) && __mips_isa_rev >= 2
     uint32_t count;
     static uint32_t cyc_per_count = 0;