diff --git a/src/crypto/chacha.c b/src/crypto/chacha.c
index ad1b3f0826..40135ed17a 100755
--- a/src/crypto/chacha.c
+++ b/src/crypto/chacha.c
@@ -42,7 +42,7 @@ void chacha(size_t doubleRounds, const void* data, size_t length, const uint8_t*
   uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
   char* ctarget = 0;
   char tmp[64];
-  int i;
+  unsigned int i;
 
   if (!length) return;