diff --git a/packages/asm/README.md b/packages/asm/README.md
index 236f83508e..b1732ee774 100644
--- a/packages/asm/README.md
+++ b/packages/asm/README.md
@@ -170,6 +170,35 @@ impossible to synthesize recursive hardware.
 }
 ```
 
+Or code that tries to include its own hash internally:
+
+```
+@myContract {
+
+   ; NOT OK! hash(hash(hash( .... (data))) will never resolve stable bytecode
+   @checksumBad[
+       {{= keccak256(myContract) }}
+   ]
+
+   ; The hash excluding of bytecode excluding the checksum works.
+   @checksumOk[
+       {{= keccak256(myContract.slice(0, checksumOk.offset)) }}
+       {{= zeroPad("0x", 32) }}
+       {{= keccak256(myContract.slice(checksumOk.offset + 32)) }}
+   ]
+
+   ; But this is fine... The source code of a file does not change
+   @checksumGood[
+      {{= id(myContract.source) }
+   ]
+
+   ; Even better; this will make disassembled code look nicer...
+   @checksumBest[
+      {{= concat([ Opcode.from("PUSH32"), id(myContract.source) ]) }
+   ]
+}
+```
+
 Building
 ========
 
diff --git a/packages/asm/src.ts/assembler.ts b/packages/asm/src.ts/assembler.ts
index 374b7eb72b..e3a8bfd7a4 100644
--- a/packages/asm/src.ts/assembler.ts
+++ b/packages/asm/src.ts/assembler.ts
@@ -14,7 +14,7 @@ import vm from "vm";
 
 import { ethers } from "ethers";
 
-import { getOpcode, Opcode } from "./opcodes";
+import { Opcode } from "./opcodes";
 
 import { parse as _parse, parser as _parser } from "./_parser";
 
@@ -61,9 +61,14 @@ class Script {
             ethers: ethers,
             utils: ethers.utils,
 
+            BigNumber: ethers.BigNumber,
+
             arrayify: ethers.utils.arrayify,
-            hexlify: ethers.utils.hexlify,
             concat: hexConcat,
+            hexlify: ethers.utils.hexlify,
+            zeroPad: function(value: ethers.utils.BytesLike, length: number) {
+                return ethers.utils.hexlify(ethers.utils.zeroPad(value, length));
+            },
 
             id: ethers.utils.id,
             keccak256: ethers.utils.keccak256,
@@ -84,7 +89,7 @@ class Script {
             formatBytes32String: ethers.utils.formatBytes32String,
             parseBytes32String: ethers.utils.parseBytes32String,
 
-            getOpcode: getOpcode,
+            Opcode: Opcode,
 
             sighash: function(signature: string): string {
                return ethers.utils.id(ethers.utils.FunctionFragment.from(signature).format()).substring(0, 10);
@@ -206,7 +211,7 @@ function pushLiteral(value: ethers.utils.BytesLike | ethers.utils.Hexable | numb
     const length = ethers.utils.hexDataLength(hex);
     if (length === 0 || length > 32) { throw new Error(`literal out of range: ${ hex }`); }
 
-    return hexConcat([ getOpcode("PUSH" + String(length)), hex ]);
+    return hexConcat([ Opcode.from("PUSH" + String(length)), hex ]);
 }
 
 export class LiteralNode extends ValueNode {
@@ -320,7 +325,7 @@ export class OpcodeNode extends ValueNode {
 
     static from(options: any): OpcodeNode {
         if (options.type !== "opcode") { throw new Error("expected opcode type"); }
-        const opcode = getOpcode(options.mnemonic);
+        const opcode = Opcode.from(options.mnemonic);
         if (!opcode) { throw new Error("unknown opcode: " + options.mnemonic); }
 
         // Using the function syntax will check the operand count
@@ -356,7 +361,7 @@ export abstract class LabelledNode extends CodeNode {
 export class LabelNode extends LabelledNode {
     async assemble(assembler: Assembler, visit: AssembleVisitFunc): Promise<void> {
         assembler.start(this);
-        visit(this, ethers.utils.hexlify(getOpcode("JUMPDEST").value));
+        visit(this, ethers.utils.hexlify(Opcode.from("JUMPDEST").value));
         assembler.end(this);
     }
 
@@ -389,7 +394,7 @@ export class DataNode extends LabelledNode {
         // Replay the data as bytecode, skipping PUSH data
         let i = 0;
         while (i < bytecode.length) {
-            const opcode = getOpcode(bytecode[i++]);
+            const opcode = Opcode.from(bytecode[i++]);
             if (opcode) {
                 i += opcode.isPush();
             }
@@ -398,7 +403,7 @@ export class DataNode extends LabelledNode {
         // The amount we overshot the data by is how much padding we need
         const padding = new Uint8Array(i - bytecode.length);
         // What makes more sense? INVALID or 0 (i.e. STOP)?
-        //padding.fill(getOpcode("INVALID").value);
+        //padding.fill(Opcode.from("INVALID").value);
         padding.fill(0);
         visit(this, ethers.utils.hexlify(padding))
 
@@ -587,7 +592,7 @@ export function disassemble(bytecode: string): Bytecode {
     let i = 0;
     let oob = false;
     while (i < bytes.length) {
-        let opcode = getOpcode(bytes[i]);
+        let opcode = Opcode.from(bytes[i]);
         if (!opcode) {
             opcode = new Opcode(`unknown (${ ethers.utils.hexlify(bytes[i]) })`, bytes[i], 0, 0);
         } else if (oob && opcode.mnemonic === "JUMPDEST") {
@@ -1017,7 +1022,7 @@ return(0, #myContract)
         return (0, 0)
 
     @checksum[
-        {{= (defines.checksum ? concat([ getOpcode("PUSH32"), id(_.source) ]): "0x") }}
+        {{= (defines.checksum ? concat([ Opcode.from("PUSH32"), id(_.source) ]): "0x") }}
     ]
 }`;
 
diff --git a/packages/asm/src.ts/index.ts b/packages/asm/src.ts/index.ts
index a3eaeee667..40299baad7 100644
--- a/packages/asm/src.ts/index.ts
+++ b/packages/asm/src.ts/index.ts
@@ -1,13 +1,12 @@
 "use strict";
 
 import { assemble, CodeNode, DataNode, disassemble, EvaluationNode, ExecutionNode, formatBytecode, LabelNode, LabelledNode, LinkNode, LiteralNode, Node, OpcodeNode, parse, ScopeNode, ValueNode } from "./assembler";
-import { getOpcode, Opcode } from "./opcodes";
+import { Opcode } from "./opcodes";
 
 import { AssemblerOptions, AssembleVisitFunc, Bytecode, Location, Operation, VisitFunc } from "./assembler";
 
 export {
     // Opcodes
-    getOpcode,
     Opcode,
 
     // Assembler functions
diff --git a/packages/asm/src.ts/opcodes.ts b/packages/asm/src.ts/opcodes.ts
index 2c2ae5023c..784f0c452d 100644
--- a/packages/asm/src.ts/opcodes.ts
+++ b/packages/asm/src.ts/opcodes.ts
@@ -55,6 +55,13 @@ export class Opcode {
     isStatic(): boolean {
         throw new Error("@TODO: return true if certain non-state-changing");
     }
+
+    static from(valueOrMnemonic: number | string) {
+        if (typeof(valueOrMnemonic) === "string") {
+            return OpcodeMap[valueOrMnemonic.toLowerCase()] || null;
+        }
+        return (Opcodes[valueOrMnemonic] || null);
+    }
 }
 
 type _Opcode = {
@@ -249,10 +256,4 @@ function repeat(char: string, length: number): string {
     return result.substring(0, length);
 }
 */
-export function getOpcode(valueOrMnemonic: number | string) {
-    if (typeof(valueOrMnemonic) === "string") {
-        return OpcodeMap[valueOrMnemonic.toLowerCase()] || null;
-    }
-    return (Opcodes[valueOrMnemonic] || null);
-}