diff --git a/ports/c/builder.js b/ports/c/builder.js
index a1c0ac5..99eaf79 100644
--- a/ports/c/builder.js
+++ b/ports/c/builder.js
@@ -661,11 +661,6 @@ class BuilderC {
 
     async _buildCircuitVar(fdData) {
 
-        const pP = fdData.pos;
-
-        const strBuff = new TextEncoder("utf-8").encode(this.header.P.toString());
-        await fdData.write(strBuff);
-
         const buff = new Uint8Array(72);
         const buffV = new DataView(buff.buffer);
 
@@ -673,7 +668,7 @@ class BuilderC {
         utils.setUint64(buffV, 8, this.pComponents, true);
         utils.setUint64(buffV, 16, this.pMapIsInput, true);
         utils.setUint64(buffV, 24, this.pConstants, true);
-        utils.setUint64(buffV, 32, pP, true);
+        utils.setUint64(buffV, 32, this.pPriemStr, true);
         utils.setUint64(buffV, 40, this.pCets, true);
 
         buffV.setUint32(48, this.header.NSignals, true);
@@ -688,6 +683,16 @@ class BuilderC {
         await fdData.write(buff);
     }
 
+    async _buildPrimeStr(fdData) {
+        this.pPriemStr = fdData.pos;
+        const strBuff = new TextEncoder("utf-8").encode(this.header.P.toString());
+        await fdData.write(strBuff);
+
+        const zB = new Uint8Array(1);
+        zB[0] =0;
+        await fdData.write(zB);
+    }
+
 
     async build(fdCode, fdData) {
         const encoder = new TextEncoder("utf-8");
@@ -696,6 +701,7 @@ class BuilderC {
 
         const code=new BigArray();
         this._buildHeader(code);
+        await this._buildPrimeStr(fdData);
         await this._buildSizes(fdData);
         await this._buildConstants(fdData);
         await this._buildHashMaps(fdData);
diff --git a/ports/wasm/build_runtime.js b/ports/wasm/build_runtime.js
index ca5a4b9..a299986 100644
--- a/ports/wasm/build_runtime.js
+++ b/ports/wasm/build_runtime.js
@@ -473,7 +473,7 @@ module.exports = function buildRuntime(module, builder) {
         );
 
         f.addCode(
-            c.if(   // If ( mapIsInput[s >> 5] & 1 << (s & 0x1f) )
+            c.if(   // If ( mapIsInput[s >> 5] & (1 << (s & 0x1f)) )
                 c.i32_and(
                     c.i32_load(
                         c.i32_add(
diff --git a/src/r1csfile.js b/src/r1csfile.js
index e5eeb94..bddb29d 100644
--- a/src/r1csfile.js
+++ b/src/r1csfile.js
@@ -8,7 +8,7 @@ module.exports.buildR1cs = buildR1cs;
 
 async function buildR1cs(ctx, fileName) {
 
-    const fd = await fastFile.createOverride(fileName, 1<<22, 1<<24);
+    const fd = await fastFile.createOverride(fileName, 1<<24, 1<<22);
 
     const buffBigInt = new Uint8Array(ctx.F.n8);