diff --git a/vendor/dragino/ldds75.js b/vendor/dragino/ldds75.js
index f5d90c2f0a..aa9cfcfb17 100644
--- a/vendor/dragino/ldds75.js
+++ b/vendor/dragino/ldds75.js
@@ -7,7 +7,7 @@ function decodeUplink(input) {
   var interrupt = input.bytes[len-1]; 
   switch (input.fPort) {
     case 2:
-  if(len==5)  
+  if(len==8)  
   {
    data.value=input.bytes[2]<<8 | input.bytes[3];
    data.distance=(value);//distance,units:mm
@@ -25,4 +25,4 @@ default:
       errors: ["unknown FPort"]
     }
 }
-}
\ No newline at end of file
+}