diff --git a/src/vm.c b/src/vm.c
index ba320d962..5facaed25 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -2310,9 +2310,9 @@ RETRY_TRY_BLOCK:
           mrb_int y = mrb_fixnum(regs[a+1]);
           double f;
           if (y == 0) {
-            if (x == 0) f = NAN;
-            else if (x > 0) f = INFINITY;
+            if (x > 0) f = INFINITY;
             else if (x < 0) f = -INFINITY;
+            else /* if (x == 0) */ f = NAN;
           }
           else {
             f = (mrb_float)x / (mrb_float)y;