diff --git a/draft-ietf-lsvr-l3dl.txt b/draft-ietf-lsvr-l3dl.txt
index 79e7ad4..e657120 100644
--- a/draft-ietf-lsvr-l3dl.txt
+++ b/draft-ietf-lsvr-l3dl.txt
@@ -658,8 +658,8 @@ Internet-Draft       Layer 3 Discovery and Liveness             May 2020
        sum[i & 3] += sbox[*b++];
      for (int i = 0; i < sizeof(sum)/sizeof(*sum); i++)
        result = (result << 8) + sum[i];
-     result = (result >> 32) + (result & 0xFFFFFFFF);
-     result = (result >> 32) + (result & 0xFFFFFFFF);
+     result = (result >> 32) + (result & 0xFFFFFFFFU);
+     result = (result >> 32) + (result & 0xFFFFFFFFU);
      return (uint32_t) result;
    }
    <CODE ENDS>
diff --git a/draft-ietf-lsvr-l3dl.xml b/draft-ietf-lsvr-l3dl.xml
index f06ccf6..13a96b1 100644
--- a/draft-ietf-lsvr-l3dl.xml
+++ b/draft-ietf-lsvr-l3dl.xml
@@ -550,8 +550,8 @@ uint32_t sbox_checksum_32(const uint8_t *b, const size_t n)
     sum[i & 3] += sbox[*b++];
   for (int i = 0; i < sizeof(sum)/sizeof(*sum); i++)
     result = (result << 8) + sum[i];
-  result = (result >> 32) + (result & 0xFFFFFFFF);
-  result = (result >> 32) + (result & 0xFFFFFFFF);
+  result = (result >> 32) + (result & 0xFFFFFFFFU);
+  result = (result >> 32) + (result & 0xFFFFFFFFU);
   return (uint32_t) result;
 }
 <CODE ENDS>