diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index 1e05e350..2c9b2a10 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -687,7 +687,9 @@ uint32_t compute_affinity_from_ip(const StringRef &ip) {
     return util::hash32(ip);
   }
 
-  return (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3];
+  return (static_cast<uint32_t>(buf[0]) << 24) |
+         (static_cast<uint32_t>(buf[1]) << 16) |
+         (static_cast<uint32_t>(buf[2]) << 8) | static_cast<uint32_t>(buf[3]);
 }
 } // namespace
 
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 3d27e6f2..f356a3fb 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -2854,8 +2854,10 @@ int compute_affinity_hash(std::vector<AffinityHash> &res, size_t idx,
     }
 
     for (int i = 0; i < 8; ++i) {
-      auto h = (buf[4 * i] << 24) | (buf[4 * i + 1] << 16) |
-               (buf[4 * i + 2] << 8) | buf[4 * i + 3];
+      auto h = (static_cast<uint32_t>(buf[4 * i]) << 24) |
+               (static_cast<uint32_t>(buf[4 * i + 1]) << 16) |
+               (static_cast<uint32_t>(buf[4 * i + 2]) << 8) |
+               static_cast<uint32_t>(buf[4 * i + 3]);
 
       res.emplace_back(idx, h);
     }