diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 923e743e..3ce00ded 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -1450,16 +1450,10 @@ utils.readVarint = function readVarint(arr, off) {
     r = utils.readU32(arr, off + 1);
     bytes = 5;
   } else if (arr[off] === 0xff) {
-    try {
-      r = utils.readU64(arr, off + 1).toNumber();
-    } catch (e) {
-      r = 0;
-    }
+    r = utils.readU64N(arr, off + 1);
     bytes = 9;
   } else {
-    // Malformed
-    r = arr[off];
-    bytes = 1;
+    assert(false, 'Malformed varint.');
   }
 
   return { off: off + bytes, r: r };
@@ -1501,7 +1495,8 @@ utils.writeVarint = function writeVarint(dst, num, off) {
   }
 
   dst[off] = 0xff;
-  utils.writeU64(dst, num, off + 1);
+  utils.writeU64N(dst, num, off + 1);
+
   return 9;
 };