diff --git a/lib/ngtcp2_cc.c b/lib/ngtcp2_cc.c
index 4b60055617e0a98e4b3ffe2a205f9233a6a2bdea..be83c1230baa5cafa34a5e5aa0cc9b0e57aa800c 100644
--- a/lib/ngtcp2_cc.c
+++ b/lib/ngtcp2_cc.c
@@ -236,7 +236,6 @@ void ngtcp2_cc_cubic_cc_free(ngtcp2_cc *cc, const ngtcp2_mem *mem) {
 static uint64_t ngtcp2_cbrt(uint64_t n) {
   int d;
   uint64_t a;
-  int i;
 
   if (n == 0) {
     return 0;
@@ -257,7 +256,7 @@ static uint64_t ngtcp2_cbrt(uint64_t n) {
 #endif
   a = 1ULL << ((64 - d) / 3 + 1);
 
-  for (i = 0; a * a * a > n; ++i) {
+  for (; a * a * a > n;) {
     a = (2 * a + n / a / a) / 3;
   }
   return a;