diff --git a/circuits/TreeUpdateArgsHasher.circom b/circuits/TreeUpdateArgsHasher.circom
index 4fb7eb0..a8306d8 100644
--- a/circuits/TreeUpdateArgsHasher.circom
+++ b/circuits/TreeUpdateArgsHasher.circom
@@ -28,18 +28,20 @@ template TreeUpdateArgsHasher(nLeaves) {
     bitsNewRoot.in <== newRoot;
     bitsPathIndices.in <== pathIndices;
 
-    hasher.in[0] <== 0;
-    hasher.in[1] <== 0;
+    var index = 0;
+
+    hasher.in[index++] <== 0;
+    hasher.in[index++] <== 0;
     for(var i = 0; i < 254; i++) {
-        hasher.in[i + 2] <== bitsOldRoot.out[253 - i];
+        hasher.in[index++] <== bitsOldRoot.out[253 - i];
     }
-    hasher.in[256] <== 0;
-    hasher.in[257] <== 0;
+    hasher.in[index++] <== 0;
+    hasher.in[index++] <== 0;
     for(var i = 0; i < 254; i++) {
-        hasher.in[i + 258] <== bitsNewRoot.out[253 - i];
+        hasher.in[index++] <== bitsNewRoot.out[253 - i];
     }
     for(var i = 0; i < 32; i++) {
-        hasher.in[i + 512] <== bitsPathIndices.out[31 - i];
+        hasher.in[index++] <== bitsPathIndices.out[31 - i];
     }
     for(var leaf = 0; leaf < nLeaves; leaf++) {
         // the range check on hash is optional, it's enforced by the smart contract anyway
@@ -49,16 +51,16 @@ template TreeUpdateArgsHasher(nLeaves) {
         bitsHash[leaf].in <== hashes[leaf];
         bitsInstance[leaf].in <== instances[leaf];
         bitsBlock[leaf].in <== blocks[leaf];
-        hasher.in[header + leaf * bitsPerLeaf + 0] <== 0;
-        hasher.in[header + leaf * bitsPerLeaf + 1] <== 0;
+        hasher.in[index++] <== 0;
+        hasher.in[index++] <== 0;
         for(var i = 0; i < 254; i++) {
-            hasher.in[header + leaf * bitsPerLeaf + i + 2] <== bitsHash[leaf].out[253 - i];
+            hasher.in[index++] <== bitsHash[leaf].out[253 - i];
         }
         for(var i = 0; i < 160; i++) {
-            hasher.in[header + leaf * bitsPerLeaf + i + 256] <== bitsInstance[leaf].out[159 - i];
+            hasher.in[index++] <== bitsInstance[leaf].out[159 - i];
         }
         for(var i = 0; i < 32; i++) {
-            hasher.in[header + leaf * bitsPerLeaf + i + 416] <== bitsBlock[leaf].out[31 - i];
+            hasher.in[index++] <== bitsBlock[leaf].out[31 - i];
         }
     }
     component b2n = Bits2Num(256);
diff --git a/package.json b/package.json
index c82ec6e..8acf5ca 100644
--- a/package.json
+++ b/package.json
@@ -42,7 +42,7 @@
   "dependencies": {
     "@openzeppelin/contracts": "^3.4.0",
     "@openzeppelin/upgrades-core": "^1.5.1",
-    "circom": "^0.5.38",
+    "circom": "0.5.42",
     "circom_runtime": "^0.1.12",
     "circomlib": "git+https://github.com/tornadocash/circomlib.git#d20d53411d1bef61f38c99a8b36d5d0cc4836aa1",
     "dotenv": "^8.2.0",
diff --git a/src/index.js b/src/index.js
index bc30643..77e8f1f 100644
--- a/src/index.js
+++ b/src/index.js
@@ -42,7 +42,14 @@ function prove(input, keyBasePath) {
         fs.writeFileSync(`${dir}/input.json`, JSON.stringify(input, null, 2))
         out = await exec(`${keyBasePath} ${dir}/input.json ${dir}/witness.json`)
       } else {
-        await wtns.calculate(utils.unstringifyBigInts(input), `${keyBasePath}.wasm`, `${dir}/witness.wtns`)
+        await wtns.debug(
+          utils.unstringifyBigInts(input),
+          `${keyBasePath}.wasm`,
+          `${dir}/witness.wtns`,
+          `${keyBasePath}.sym`,
+          {},
+          console,
+        )
         const witness = utils.stringifyBigInts(await wtns.exportJson(`${dir}/witness.wtns`))
         fs.writeFileSync(`${dir}/witness.json`, JSON.stringify(witness, null, 2))
       }
diff --git a/yarn.lock b/yarn.lock
index e1d0373..ee1dee7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2241,10 +2241,10 @@ circom@0.5.33:
     tmp-promise "^2.0.2"
     wasmbuilder "0.0.10"
 
-circom@^0.5.38:
-  version "0.5.38"
-  resolved "https://registry.yarnpkg.com/circom/-/circom-0.5.38.tgz#c099fb196085837575fb266f37b0516b1ec56eb5"
-  integrity sha512-PFlXto8gDysUlwk6z/GYbn1Mv5BtW9BI4769N9gSP0/7KDNSqLNyVmL4DgMLc67/EpG4qJLGch3SdgzQD+/cfw==
+circom@0.5.42:
+  version "0.5.42"
+  resolved "https://registry.yarnpkg.com/circom/-/circom-0.5.42.tgz#96a456f9538f4425654df091d15e3158e9da2acc"
+  integrity sha512-v6+f9g3z2ia17NQvQmyZjvh8cE8O3GtxRE36KfJfx/a+s58Y7aEDWsUG+GFRJhp1ajiQELdj3NehY9vHSf5Rkg==
   dependencies:
     chai "^4.2.0"
     circom_runtime "0.1.12"