diff --git a/hmac-sha256.c b/hmac-sha256.c
index 714933f..f7cf7ba 100644
--- a/hmac-sha256.c
+++ b/hmac-sha256.c
@@ -29,7 +29,7 @@ void hmac_sha256_init(hmac_sha256_ctx_t *s, void* key, uint16_t kl){
 	if (kl > SHA256_BLOCK_BITS){
 		sha256((void*)buffer, key, kl);
 	} else {
-		memcpy(buffer, key, (kl+7/8));
+		memcpy(buffer, key, (kl+7)/8);
 	}
 	
 	for (i=0; i<SHA256_BLOCK_BITS/8; ++i){