diff --git a/src/sim/simulate.cc b/src/sim/simulate.cc
--- a/src/sim/simulate.cc
+++ b/src/sim/simulate.cc
@@ -51,7 +51,7 @@
 
     if (num_cycles < 0)
         fatal("simulate: num_cycles must be >= 0 (was %d)\n", num_cycles);
-    else if (curTick() + num_cycles < 0)  //Overflow
+    else if (MaxTick - curTick() <= num_cycles) //Overflow
         num_cycles = MaxTick;
     else
         num_cycles = curTick() + num_cycles;