diff --git a/convex-core/src/main/java/convex/core/cvm/AOp.java b/convex-core/src/main/java/convex/core/cvm/AOp.java
index 87d392d3c..136b6b3ab 100644
--- a/convex-core/src/main/java/convex/core/cvm/AOp.java
+++ b/convex-core/src/main/java/convex/core/cvm/AOp.java
@@ -51,13 +51,6 @@ public ACell toCanonical() {
 		return this;
 	}
 
-	/**
-	 * Returns the opcode for this op
-	 * 
-	 * @return Opcode as a byte
-	 */
-	public abstract byte opCode();
-
 	@Override
 	public final int encode(byte[] bs, int pos) {
 		bs[pos++]=getTag();
@@ -70,6 +63,10 @@ public int encodeRaw(byte[] bs, int pos) {
 		return encodeAfterOpcode(bs,pos);
 	}
 
+	protected byte opCode() {
+		return 0;
+	}
+
 	/**
 	 * Writes the raw data for this Op to the specified bytebuffer. Assumes Op tag
 	 * and opcode already written.
diff --git a/convex-core/src/main/java/convex/core/cvm/Ops.java b/convex-core/src/main/java/convex/core/cvm/Ops.java
index 9374048c1..2c16f8e68 100644
--- a/convex-core/src/main/java/convex/core/cvm/Ops.java
+++ b/convex-core/src/main/java/convex/core/cvm/Ops.java
@@ -22,14 +22,10 @@ public class Ops {
 	public static final byte TRY = 3;
 	public static final byte LET = 4;
 	public static final byte LOOP = 5;
-	public static final byte DEF = 6;
 	public static final byte LOOKUP = 7;
 	public static final byte LAMBDA = 8;
 	public static final byte QUERY = 9;
-	public static final byte LOCAL=10;
-	public static final byte SET = 11;
 	
-	public static final byte SPECIAL = 15;
 	// public static final byte CALL = 9;
 	// public static final byte RETURN = 10;
 
@@ -59,14 +55,16 @@ public static <T extends ACell> AOp<T> read(byte tag, Blob b, int pos) throws Ba
 		case Ops.LOOKUP:
 			return Lookup.read(b,pos);
 		case CVMTag.OPCODE_LAMBDA:
-			return (AOp<T>) Lambda.read(b,pos);
+			return (AOp<T>) Lambda.read(b,pos); 
 		case Ops.LET:
 			return Let.read(b,pos,false);
 		case Ops.QUERY:
 			return Query.read(b,pos);
 		case Ops.LOOP:
 			return Let.read(b,pos,true);
-		case Ops.SET:
+		
+		// These tags mean we must have a Long integer, which resolves to a Set operation
+		case 0x10: case 0x11: case 0x12: case 0x13: case 0x14: case 0x15: case 0x16: case 0x17: case 0x18:
 			return Set.read(b,pos);
 
 		default:
diff --git a/convex-core/src/main/java/convex/core/cvm/ops/Def.java b/convex-core/src/main/java/convex/core/cvm/ops/Def.java
index 48a56bcf1..9b37292d0 100644
--- a/convex-core/src/main/java/convex/core/cvm/ops/Def.java
+++ b/convex-core/src/main/java/convex/core/cvm/ops/Def.java
@@ -4,7 +4,6 @@
 import convex.core.cvm.CVMTag;
 import convex.core.cvm.Context;
 import convex.core.cvm.Juice;
-import convex.core.cvm.Ops;
 import convex.core.cvm.Syntax;
 import convex.core.data.ACell;
 import convex.core.data.Blob;
@@ -100,11 +99,6 @@ public boolean print(BlobBuilder sb, long limit) {
 		return sb.check(limit);
 	}
 
-	@Override
-	public byte opCode() {
-		return Ops.DEF;
-	}
-
 	@Override
 	public int estimatedEncodingSize() {
 		return 100;
diff --git a/convex-core/src/main/java/convex/core/cvm/ops/Local.java b/convex-core/src/main/java/convex/core/cvm/ops/Local.java
index 2576ead5a..27b87f90b 100644
--- a/convex-core/src/main/java/convex/core/cvm/ops/Local.java
+++ b/convex-core/src/main/java/convex/core/cvm/ops/Local.java
@@ -5,7 +5,6 @@
 import convex.core.cvm.CVMTag;
 import convex.core.cvm.Context;
 import convex.core.cvm.Juice;
-import convex.core.cvm.Ops;
 import convex.core.data.ACell;
 import convex.core.data.AVector;
 import convex.core.data.Format;
@@ -55,11 +54,6 @@ public Context execute(Context ctx) {
 		T result = (T)env.get(position);
 		return ctx.withResult(Juice.LOOKUP,result);
 	}
-
-	@Override
-	public byte opCode() {
-		return Ops.LOCAL;
-	}
 	
 	@Override
 	public byte getTag() {
diff --git a/convex-core/src/main/java/convex/core/cvm/ops/Set.java b/convex-core/src/main/java/convex/core/cvm/ops/Set.java
index c001fc1c0..95f7591d2 100644
--- a/convex-core/src/main/java/convex/core/cvm/ops/Set.java
+++ b/convex-core/src/main/java/convex/core/cvm/ops/Set.java
@@ -2,6 +2,7 @@
 
 import convex.core.ErrorCodes;
 import convex.core.cvm.AOp;
+import convex.core.cvm.CVMTag;
 import convex.core.cvm.Context;
 import convex.core.cvm.Juice;
 import convex.core.cvm.Ops;
@@ -10,33 +11,31 @@
 import convex.core.data.Blob;
 import convex.core.data.Cells;
 import convex.core.data.Format;
-import convex.core.data.IRefFunction;
 import convex.core.data.Ref;
+import convex.core.data.prim.CVMLong;
 import convex.core.data.util.BlobBuilder;
 import convex.core.exceptions.BadFormatException;
 import convex.core.exceptions.InvalidDataException;
-import convex.core.util.ErrorMessages;
 
 /**
  * Op to set a lexical value in the local execution context. i.e. `set!`
  *
  * @param <T> Result type of Op
  */
-public class Set<T extends ACell> extends AOp<T> {
+public class Set<T extends ACell> extends ACodedOp<T,CVMLong,AOp<T>> {
 
 	/**
 	 * Stack position in lexical stack
 	 */
 	private final long position;
 
-	/**
-	 * Op to compute new value
-	 */
-	private final Ref<AOp<T>> op;
-
+	public Set(Ref<CVMLong> code, Ref<AOp<T>> value) {
+		super(CVMTag.OP_CODED,code,value);
+		this.position = code.getValue().longValue(); // safe because always embedded
+	}
+	
 	private Set(long position, Ref<AOp<T>> op) {
-		this.position = position;
-		this.op = op;
+		this(CVMLong.create(position).getRef(),op);
 	}
 
 	/**
@@ -59,7 +58,7 @@ public Context execute(Context ctx) {
 			return ctx.withError(ErrorCodes.BOUNDS, "Bad position for set!: " + position);
 		}
 
-		ctx = ctx.execute(op.getValue());
+		ctx = ctx.execute(value.getValue());
 		if (ctx.isExceptional()) return ctx;
 		ACell value = ctx.getResult();
 
@@ -68,18 +67,6 @@ public Context execute(Context ctx) {
 		return ctx.consumeJuice(Juice.SET_BANG);
 	}
 
-	@Override
-	public byte opCode() {
-		return Ops.SET;
-	}
-
-	@Override
-	public int encodeAfterOpcode(byte[] bs, int pos) {
-		pos = Format.writeVLQLong(bs, pos, position);
-		pos = op.encode(bs,pos);
-		return pos;
-	}
-
 	/**
 	 * Reads a Set Op from a Blob encoding
 	 * 
@@ -103,44 +90,27 @@ public static <R extends ACell> Set<R> read(Blob b, int pos) throws BadFormatExc
 		return result;
 	}
 
-	@Override
-	public Set<T> updateRefs(IRefFunction func) {
-		@SuppressWarnings("unchecked")
-		Ref<AOp<T>> newOp = (Ref<AOp<T>>) func.apply(op);
-		if (op == newOp) return this;
-		return new Set<T>(position, newOp);
-	}
-
 	@Override
 	public void validateCell() throws InvalidDataException {
-		if (op == null) {
-			throw new InvalidDataException("Null Set op ", this);
-		}
 		if (position < 0) {
 			throw new InvalidDataException("Invalid Local position " + position, this);
 		}
 	}
 
-	@Override
-	public int getRefCount() {
-		return 1;
-	}
-
-	@SuppressWarnings("unchecked")
-	@Override
-	public Ref<AOp<T>> getRef(int i) {
-		if (i != 0) throw new IndexOutOfBoundsException(ErrorMessages.badIndex(i));
-		return op;
-	}
-
 	@Override
 	public boolean print(BlobBuilder sb, long limit) {
 		sb.append("(set! %");
 		sb.append(Long.toString(position));
 		sb.append(' ');
-		if (!op.getValue().print(sb, limit)) return false;
+		if (!value.getValue().print(sb, limit)) return false;
 		sb.append(')');
 		return sb.check(limit);
 	}
 
+	@Override
+	protected AOp<T> rebuild(Ref<CVMLong> newCode, Ref<AOp<T>> newValue) {
+		if ((newCode==code)&&(newValue==value)) return this;
+		return new Set<T>(newCode,newValue);
+	}
+
 }
diff --git a/convex-core/src/main/java/convex/core/cvm/ops/Special.java b/convex-core/src/main/java/convex/core/cvm/ops/Special.java
index 92028dbff..9a18602c3 100644
--- a/convex-core/src/main/java/convex/core/cvm/ops/Special.java
+++ b/convex-core/src/main/java/convex/core/cvm/ops/Special.java
@@ -147,11 +147,6 @@ public Context execute(Context ctx) {
 		}
 		return ctx.consumeJuice(Juice.SPECIAL);
 	}
-
-	@Override
-	public byte opCode() {
-		return Ops.SPECIAL;
-	}
 	
 	@Override
 	public byte getTag() {
diff --git a/convex-core/src/test/java/convex/core/lang/OpsTest.java b/convex-core/src/test/java/convex/core/lang/OpsTest.java
index 405d3ae27..bc34e4fb7 100644
--- a/convex-core/src/test/java/convex/core/lang/OpsTest.java
+++ b/convex-core/src/test/java/convex/core/lang/OpsTest.java
@@ -213,7 +213,7 @@ public void testSpecial() {
 	@Test
 	public void testSet() throws BadFormatException {
 		AOp<Address> op = Set.create(45, Constant.nil());
-		Blob expectedEncoding=Blob.fromHex("c00b2dc0b000");
+		Blob expectedEncoding=Blob.fromHex("c0112dc0b000");
 		assertEquals(expectedEncoding,op.getEncoding());
 		assertEquals(op,Format.read(expectedEncoding));
 		doOpTest(op);