diff --git a/src/exec.js b/src/exec.js
index a280a28..cd5b9d3 100644
--- a/src/exec.js
+++ b/src/exec.js
@@ -547,15 +547,17 @@ function execFor(ctx, ast) {
     let v = exec(ctx, ast.condition);
     if (ctx.error) return;
 
-    while ((v.value.neq(0))&&(!ctx.returnValue)) {
-        exec(ctx, ast.body);
-        if (ctx.error) return;
+    if (typeof v.value != "undefined") {
+        while ((v.value.neq(0))&&(!ctx.returnValue)) {
+            exec(ctx, ast.body);
+            if (ctx.error) return;
 
-        exec(ctx, ast.step);
-        if (ctx.error) return;
+            exec(ctx, ast.step);
+            if (ctx.error) return;
 
-        v = exec(ctx, ast.condition);
-        if (ctx.error) return;
+            v = exec(ctx, ast.condition);
+            if (ctx.error) return;
+        }
     }
 }
 
@@ -563,12 +565,14 @@ function execWhile(ctx, ast) {
     let v = exec(ctx, ast.condition);
     if (ctx.error) return;
 
-    while ((v.value.neq(0))&&(!ctx.returnValue)) {
-        exec(ctx, ast.body);
-        if (ctx.error) return;
+    if (typeof v.value != "undefined") {
+        while ((v.value.neq(0))&&(!ctx.returnValue)) {
+            exec(ctx, ast.body);
+            if (ctx.error) return;
 
-        v = exec(ctx, ast.condition);
-        if (ctx.error) return;
+            v = exec(ctx, ast.condition);
+            if (ctx.error) return;
+        }
     }
 }
 
@@ -576,13 +580,15 @@ function execIf(ctx, ast) {
     let v = exec(ctx, ast.condition);
     if (ctx.error) return;
 
-    if ((v.value.neq(0))&&(!ctx.returnValue)) {
-        exec(ctx, ast.then);
-        if (ctx.error) return;
-    } else {
-        if (ast.else) {
-            exec(ctx, ast.else);
+    if (typeof v.value != "undefined") {
+        if ((v.value.neq(0))&&(!ctx.returnValue)) {
+            exec(ctx, ast.then);
             if (ctx.error) return;
+        } else {
+            if (ast.else) {
+                exec(ctx, ast.else);
+                if (ctx.error) return;
+            }
         }
     }
 }
diff --git a/test/cases.js b/test/cases.js
new file mode 100644
index 0000000..49df23f
--- /dev/null
+++ b/test/cases.js
@@ -0,0 +1,14 @@
+const chai = require("chai");
+const path = require("path");
+const snarkjs = require("snarkjs");
+const crypto = require("crypto");
+
+const compiler = require("../index.js");
+
+const assert = chai.assert;
+
+describe("Sum test", () => {
+    it("Should compile a code with an undefined if", async() => {
+        await compiler(path.join(__dirname, "circuits", "undefinedif.circom"));
+    });
+});
diff --git a/test/circuits/undefinedif.circom b/test/circuits/undefinedif.circom
new file mode 100644
index 0000000..ec117f8
--- /dev/null
+++ b/test/circuits/undefinedif.circom
@@ -0,0 +1,14 @@
+template X() {
+    signal input i;
+    signal input j;
+    signal output out;
+
+    if (i == 0) {
+        out <-- i;
+    }
+    else {
+        out <-- j;
+    }
+}
+
+component main = X();