diff --git a/java/src/json/ext/SWARBasicStringEncoder.java b/java/src/json/ext/SWARBasicStringEncoder.java
index 08cd2e47..02a3bfcd 100644
--- a/java/src/json/ext/SWARBasicStringEncoder.java
+++ b/java/src/json/ext/SWARBasicStringEncoder.java
@@ -23,9 +23,13 @@ void encode(ByteList src) throws IOException {
         int beg = 0;
         int pos = 0;
 
-        ByteBuffer bb = ByteBuffer.wrap(ptrBytes, 0, len);
-        while (ptr + pos + 8 <= len) {
-            long x = bb.getLong(ptr + pos);
+        // There are optimizations in JRuby where ptr > 0 will be true. For example, if we 
+        // slice a string, the underlying byte array is the same, but the
+        // begin index and real size are different. When reading from the ptrBytes
+        // array, we need to always add ptr to the index.
+        ByteBuffer bb = ByteBuffer.wrap(ptrBytes, ptr, len);
+        while (pos + 8 <= len) {
+            long x = bb.getLong(pos);
             if (skipChunk(x)) {
                 pos += 8;
                 continue;
@@ -43,8 +47,8 @@ void encode(ByteList src) throws IOException {
             }
         }
 
-        if (ptr + pos + 4 <= len) {
-            int x = bb.getInt(ptr + pos);
+        if (pos + 4 <= len) {
+            int x = bb.getInt(pos);
             if (skipChunk(x)) {
                 pos += 4;
             }