diff --git a/test/utest.cpp b/test/utest.cpp
index 279417a..d436179 100644
--- a/test/utest.cpp
+++ b/test/utest.cpp
@@ -143,7 +143,8 @@
     char mdString[EVP_MAX_MD_SIZE * 2 + 1];
     for (decltype(digest_count) i = 0; i < digest_count; i++)
     {
-        snprintf(&mdString[i * 2], 3, "%02x", (unsigned int)digest[i]);
+        snprintf(&mdString[static_cast<size_t>(i) * 2], 3, "%02x",
+                 (unsigned int)digest[i]);
     }
     std::string hexId = std::string(mdString);
     hexId = hexId.substr(0, 8);