diff --git a/lib/bcoin/script.js b/lib/bcoin/script.js
index bbc3006c..cc05972a 100644
--- a/lib/bcoin/script.js
+++ b/lib/bcoin/script.js
@@ -2814,6 +2814,8 @@ Script.encode = function encode(code) {
           p.writeU8(opcodes.OP_PUSHDATA4);
           p.writeU32(op.pushdata.size);
           p.writeBytes(op);
+        } else {
+          assert(false, 'Bad pushdata op.');
         }
         continue;
       }
@@ -2821,6 +2823,18 @@ Script.encode = function encode(code) {
       if (op.length === 0) {
         p.writeU8(opcodes.OP_0);
       } else if (op.length <= 0x4b) {
+        if (op.length === 1) {
+          if (op[0] === 0) {
+            p.writeU8(opcodes.OP_0);
+            continue;
+          } else if (op[0] >= 1 && op[0] <= 16) {
+            p.writeU8(op[0] + 0x50);
+            continue;
+          } else if (op[0] === 0xff) {
+            p.writeU8(opcodes.OP_1NEGATE);
+            continue;
+          }
+        }
         p.writeU8(op.length);
         p.writeBytes(op);
       } else if (op.length <= 0xff) {
@@ -2831,10 +2845,12 @@ Script.encode = function encode(code) {
         p.writeU8(opcodes.OP_PUSHDATA2);
         p.writeU16(op.length);
         p.writeBytes(op);
-      } else {
+      } else if (op.length <= 0xffffffff) {
         p.writeU8(opcodes.OP_PUSHDATA4);
         p.writeU32(op.length);
         p.writeBytes(op);
+      } else {
+        assert(false, 'Bad pushdata op.');
       }
       continue;
     }
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 475289ce..76684f36 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -1501,7 +1501,7 @@ utils.writeVarint = function writeVarint(dst, num, off) {
   off = off >>> 0;
 
   if (bn.isBN(num)) {
-    if (num.cmpn(0xffffffff) > 0) {
+    if (num.cmp(utils.U32) > 0) {
       dst[off] = 0xff;
       utils.writeU64(dst, num, off + 1);
       return 9;
@@ -1540,7 +1540,7 @@ utils.writeVarint = function writeVarint(dst, num, off) {
 
 utils.sizeVarint = function sizeVarint(num) {
   if (bn.isBN(num)) {
-    if (num.cmpn(0xffffffff) > 0)
+    if (num.cmp(utils.U32) > 0)
       return 9;
     num = num.toNumber();
   }