diff --git a/ChangeLog b/ChangeLog
index 2bac81fc4..e6a2c2f76 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,7 @@
              - Handle out of memory errors in jsvCreateNewChild
              - Do not garbage collect inside an IRQ
             On nRF52 devices, allow button press at boot to clear out peer manager data
+            Work out length of typed array with offset correctly (fix #1204)
 
      1v93 : Ensure that specifying too many advertising UUIDs causes an exception, not a reboot
             nRF5x: Fix for time jump caused by reentrancy in jshGetSystemTime
diff --git a/src/jswrap_arraybuffer.c b/src/jswrap_arraybuffer.c
index 61bce3d95..827672fc8 100644
--- a/src/jswrap_arraybuffer.c
+++ b/src/jswrap_arraybuffer.c
@@ -337,7 +337,10 @@ JsVar *jswrap_typedarray_constructor(JsVarDataArrayBufferViewType type, JsVar *a
     jsExceptionHere(JSET_ERROR, "Unsupported first argument of type %t\n", arr);
     return 0;
   }
-  if (length==0) length = (JsVarInt)(jsvGetArrayBufferLength(arrayBuffer) / JSV_ARRAYBUFFER_GET_SIZE(type));
+  if (length==0) {
+    length = (JsVarInt)((jsvGetArrayBufferLength(arrayBuffer)-byteOffset) / JSV_ARRAYBUFFER_GET_SIZE(type)); 
+    if (length<0) length=0;
+  }
   JsVar *typedArr = jsvNewWithFlags(JSV_ARRAYBUFFER);
   if (typedArr) {
     typedArr->varData.arraybuffer.type = type;