diff --git a/src/video/e_pow.h b/src/video/e_pow.h
index d87348d72..62fc989ce 100644
--- a/src/video/e_pow.h
+++ b/src/video/e_pow.h
@@ -208,7 +208,7 @@ __ieee754_pow(x, y)
             return (hy > 0) ? huge * huge : tiny * tiny;
         /* now |1-x| is tiny <= 2**-20, suffice to compute
            log(x) by x-x^2/2+x^3/3-x^4/4 */
-        t = x - 1;              /* t has 20 trailing zeros */
+        t = ax - 1;             /* t has 20 trailing zeros */
         w = (t * t) * (0.5 - t * (0.3333333333333333333333 - t * 0.25));
         u = ivln2_h * t;        /* ivln2_h has 21 sig. bits */
         v = t * ivln2_l - w * ivln2;