diff --git a/js/experimental/runtime/kernel/reader.js b/js/experimental/runtime/kernel/reader.js
index 2b80e15bff..44708b5aec 100644
--- a/js/experimental/runtime/kernel/reader.js
+++ b/js/experimental/runtime/kernel/reader.js
@@ -97,19 +97,6 @@ function readSfixed64(bufferDecoder, start) {
   return Int64.fromBits(lowBits, highBits);
 }
 
-/**
- * Reads a sint32 value from the binary bytes encoded as varint.
- * @param {!BufferDecoder} bufferDecoder Binary format encoded bytes.
- * @param {number} start Start of the data.
- * @return {number}
- * @package
- */
-function readSint32(bufferDecoder, start) {
-  const bits = bufferDecoder.getUnsignedVarint32At(start);
-  // Truncate upper bits and convert from zig zag to signd int
-  return (bits >>> 1) ^ -(bits & 0x01);
-}
-
 /**
  * Reads a sint64 value from the binary bytes encoded as varint.
  * @param {!BufferDecoder} bufferDecoder Binary format encoded bytes.
@@ -125,6 +112,17 @@ function readSint64(bufferDecoder, start) {
   return Int64.fromBits(decodedLowerBits, decodedUpperBits);
 }
 
+/**
+ * Reads a sint32 value from the binary bytes encoded as varint.
+ * @param {!BufferDecoder} bufferDecoder Binary format encoded bytes.
+ * @param {number} start Start of the data.
+ * @return {number}
+ * @package
+ */
+function readSint32(bufferDecoder, start) {
+  return readSint64(bufferDecoder, start).getLowBits();
+}
+
 /**
  * Read a subarray of bytes representing a length delimited field.
  * @param {!BufferDecoder} bufferDecoder Binary format encoded bytes.