diff --git a/package.json b/package.json
index 50a309b..b2fdb89 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,7 @@
     "chai": "^4.2.0",
     "circom_runtime": "0.0.3",
     "ffiasm": "0.0.2",
-    "ffjavascript": "0.0.3",
+    "ffjavascript": "0.0.4",
     "ffwasm": "0.0.6",
     "fnv-plus": "^1.3.1",
     "r1csfile": "0.0.3",
diff --git a/src/construction_phase.js b/src/construction_phase.js
index 2736e86..88f7981 100644
--- a/src/construction_phase.js
+++ b/src/construction_phase.js
@@ -624,6 +624,9 @@ function execReturn(ctx, ast) {
 function execVariable(ctx, ast) {
 
     const v = ctx.refs[ast.refId];
+    if (!v) {
+        return ctx.throwError(ast, "Variable not defined: "+ast.name);
+    }
 
     const sels = [];
     for (let i=0; i< ast.selectors.length; i++) {
diff --git a/src/gencode.js b/src/gencode.js
index c2e629e..b9be071 100644
--- a/src/gencode.js
+++ b/src/gencode.js
@@ -175,17 +175,17 @@ function gen(ctx, ast) {
         } else if (ast.op == ">>") {
             return genOp(ctx, ast, "shr", 2);
         } else if (ast.op == "<") {
-            return genOp(ctx, ast, "lt", 2);
+            return genOp(ctx, ast, "lt", 2, true);
         } else if (ast.op == ">") {
-            return genOp(ctx, ast, "gt", 2);
+            return genOp(ctx, ast, "gt", 2, true);
         } else if (ast.op == "<=") {
-            return genOp(ctx, ast, "leq", 2);
+            return genOp(ctx, ast, "leq", 2, true);
         } else if (ast.op == ">=") {
-            return genOp(ctx, ast, "geq", 2);
+            return genOp(ctx, ast, "geq", 2, true);
         } else if (ast.op == "==") {
-            return genOp(ctx, ast, "eq", 2);
+            return genOp(ctx, ast, "eq", 2, true);
         } else if (ast.op == "!=") {
-            return genOp(ctx, ast, "neq", 2);
+            return genOp(ctx, ast, "neq", 2, true);
         } else if (ast.op == "?") {
             return genTerCon(ctx, ast);
         } else {
@@ -1121,7 +1121,7 @@ function genOpOp(ctx, ast, op, lr) {
     }
 }
 
-function genOp(ctx, ast, op, nOps) {
+function genOp(ctx, ast, op, nOps, adjustBool) {
     const vals = [];
     const valRefs = [];
 
@@ -1159,7 +1159,8 @@ function genOp(ctx, ast, op, nOps) {
         for (let i=0; i<nOps; i++) {
             params.push(vals[i].value[0]);
         }
-        rRef = newRef(ctx, "BIGINT", "_tmp", ctx.field[op](...params));
+
+        rRef = newRef(ctx, "BIGINT", "_tmp", adjustBool ? (ctx.field[op](...params)?bigInt.one:bigInt.zero)  : ctx.field[op](...params));
     }
     return rRef;
 }
diff --git a/src/lcalgebra.js b/src/lcalgebra.js
index 5ed8c43..914e927 100644
--- a/src/lcalgebra.js
+++ b/src/lcalgebra.js
@@ -85,12 +85,6 @@ class LCAlgebra {
         const self = this;
         this.field= aField;
         [
-            ["lt",2],
-            ["leq",2],
-            ["eq",2],
-            ["neq",2],
-            ["geq",2],
-            ["gt",2],
             ["idiv",2],
             ["mod",2],
             ["band",2],
@@ -102,12 +96,18 @@ class LCAlgebra {
             ["lnot",2],
             ["shl",2],
             ["shr",2],
+            ["lt",2, true],
+            ["leq",2, true],
+            ["eq",2, true],
+            ["neq",2, true],
+            ["geq",2, true],
+            ["gt",2, true]
         ].forEach( (op) => {
-            self._genNQOp(op[0], op[1]);
+            self._genNQOp(op[0], op[1], op[2]);
         });
     }
 
-    _genNQOp(op, nOps) {
+    _genNQOp(op, nOps, adjustBool) {
         const self=this;
         self[op] = function() {
             const operands = [];
@@ -118,7 +118,7 @@ class LCAlgebra {
             }
             return {
                 t: "N",
-                v: self.field[op](...operands)
+                v: adjustBool ? ( self.field[op](...operands) ? bigInt.one: bigInt.zero) : self.field[op](...operands)
             };
         };
     }
diff --git a/src/utils.js b/src/utils.js
index f8748da..85936cf 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -77,7 +77,7 @@ function fnvHash(str) {
 
 
 function stringifyBigInts(o) {
-    if ((typeof(o) == "bigint") || o.isZero !== undefined)  {
+    if ((typeof(o) == "bigint") || o.eq !== undefined)  {
         return o.toString(10);
     } else if (Array.isArray(o)) {
         return o.map(stringifyBigInts);